Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR SECURING DATA COMMUNICATION
Field of the Invention
The present invention is directed to methods
and apparatus for communicating data, telecommunications
access methods, and, more particularly, to auto-dialers,
security and information devices that can transmit and
receive data.
Background of the Invention
In the modern world, telephone transactions
involving extensions of credit, payment of bills, fund
transfers and the providing of other types of se prices
are commonplace. Generally, such services are provided
in response to a user dialing the telephone number of a
service and by then entering identification information
and/or credit card information using standard "touch
tones", i.e., dual tone mufti-frequency signals ("DTMF
tones"), to represent the identification information
being entered and transmitted. Normally, such touch tone
signals are produced using a standard telephone keypad
input device.
Touch tones are generated using a dual tone
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multi-frequency (DTMF) encoding technique, as opposed to
a frequency shift key (FSK) encoding, which is frequently
used for data transmission purposes. In accordance with
the DTMF technique used to generate touch tone signals,
tone signals are produced by generating two tones such
that one tone is selected from a high frequency band
group and the other tone is selected from a low frequency
band group. In standard telephone systems, the high
frequency band group includes four high frequencies
(1209, 1336, 1477, and 1633 Hz) while the low band
frequency group includes four low frequencies (697, 770,
852 and 941 Hz). Each of the high and low frequencies is
referred to as a fundamental frequency.
Each one of the low frequencies corresponds to
one of the four rows of keys on a standard extended
telephone keypad while each one of the four high
frequencies corresponds to one of the four columns of
keys on standard extended telephone keypads.
Accordingly, low frequency tones represent row tones and
high frequency tones represent column tones. It should
be noted that extended and non-extended keypads differ in
that extended keypads include the additional fourth
column of keys not found on non-extended standard keypads
such as those commonly used with public telephones and
household telephones, although these additional tones are
found in most modem hardware/software systems.
Each different telephone key is represented by
a signal including a unique combination of one tone from
the high band and one from the low band. Sixteen
different signal states may be represented by this
encoding technique with one signal state corresponding to
each one of the sixteen keys that can be found on a
standard telephone keypad. Referring now to Fig. 8A,
there is illustrated a chart which lists the 16 different
numbers/symbols that are represented by the 16 different
signal states and the Hi-tone and Lo-tone frequency
associated with each of the 16 different signal states.
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A received DTMF tone signal is determined, in
telephone switching and DTMF tone signal detection
devices, as having a valid signal state if five
conditions are met. The first of these is that the tone
signal contain exactly one valid tone, and only one valid
tone, from each of the low and high band frequency
groups, i.e., the signal must contain only one valid Hi-
tone and one valid Lo-tone frequency. The second
condition is that the low and high tones are present for
a predetermined minimum time duration, i.e., at least 35-
40 milliseconds. Third, the difference in amplitude
(level), commonly referred to as "twist", between the low
and the high tone must fall within a predetermined range,
i.e., the Hi-band tone signal power level can not be
greater than 4 dBm more or 8 dHm less than the Lo-band
tone signal power level, where dBm is a logarithmic
measure of power with respect to a reference power of 1
milliwatt. Fourth, the amplitude level of each tone
signal in the tone pair must be in the range of 0 to -25
dBm. Fifth, consecutive tone-pairs must be separated by a
period of silence for at least 35-40 milliseconds.
Thus, if too many or too few tones are detected
the detection criteria will not be met and a valid signal
state will not be indicated. When a valid signal state
does occur, the particular combination of low and high
tones is decoded to produce an indication of the
corresponding key or signal state that was responsible
for the generation of the DTMF tone signal. It is this
key or signal state information that represents, e.g.,
one of the numerical digits comprising a telephone or
credit card number.
Placing a voice call, using a calling card
number or other credit card number, is exemplary of one
of the most common types of telephone credit transactions
involving the use of DTMF tones.
Referring now to Fig. 1, there is illustrated a
flow chart 9, generally represented by the reference
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numeral 1000, illustrating a standard telephone call
transaction involving the use of a credit card for
billing purposes. As illustrated, the standard telephone
call transaction comprises the first step of making a
S decision to place a credit card call 1001 followed by the
actual step of dialing 1002. As part of the dialing step
1002 a user enters, using, e.g., the telephone keypad, an
access code identifying the desired long distance
telephone carrier, and a destination number, i.e., the
telephone number of the party being called. Both the
access code and telephone number are represented as DTMF
tones, i.e., touch tones, generated by the telephone in
response to the keypad input.
The telephone system, e.g., the local switching
office to which the telephone is linked, connects the
callex to the appropriate long distance carrier
represented by the access code input by the user. The
long distance carrier then generates an audible
signal/message indicating to the caller that it is ready
to receive billing information as indicated in step 1003.
In response to the audible signal/message
generated by the long distance carrier, the caller then
inputs, e.g., using the telephone keypad, a credit card
number as illustrated in step 1004. In response to
receiving DTMF tones representing the credit card number,
generated by the telephone, the long distance carrier
checks the credit card number for validity as illustrated
in step 1006. If the credit card number is determined to
be valid, the call is placed as illustrated in step 1008.
However, if the credit card number is determined to be
invalid, the call is rejected and the telephone
connection is disconnected as illustrated in step 1010.
The standard procedure for placing a call using
a credit card has several drawbacks. For example,
requiring a caller to manually input through the
telephone keypad a carrier access number, a destination
number, and a credit card number introduces into the
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calling procedure ample opportunity for a user to
accidentally input an incorrect number for any one of th=
required values, which can exceed, e.g., 35 required
inputs- more if the call is placed to or from a foreign
5 country.
It is generally understood that the likelihood
of entry errors increases in proportion to the number o.
digits to be entered. Such an error normally results in
the call being rejected by the telephone carrier,
requiring the caller to repeat the entire calling
procedure from the point of connection to the long
distance carrier. Generally, the long distance carrier
pays fees to the company which owns the originating local
switching office of the caller from the moment of
connection, and is unable to start billing for the
ultimate connection until the moment of connection. In
such a case, each entry error is an increase in the
unbillable time that a long distance carrier must absorb
without any offsetting revenue.
Generally, the requirement that a caller
manually input a large series of numbers to place a call
leads to a higher error rate during call placement than
results when the caller has to input fewer numbers, e.g.,
when calls are placed without the use of credit cards.
In addition, requiring a caller to manually input a
calling card number discourages some callers from using a
credit card to place a call because of the additional
time and frequent input errors associated with the
initiation of a call as compared to calls placed without
using credit cards.
In addition to error problems associated with
the manual input of credit card number information,
security problems are also associated with the manual
input of credit card data into a telephone using a
standard keypad. For example, a person viewing the
initiation of a telephone transaction can record the
credit card number input to the telephone keypad and the.~_
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later use the calling card number to place unauthorized
calls.
Portable electronic information cards and auto-
dialers that are capable of being acoustically coupled to
telephone systems to perform dialing functions are well
known in the art.
Such known devices which generate a series of
DTMF tones representing the numbers which must be input
to initiate a call, have reduced or eliminated the need
to input telephone number, carrier number, and credit
card number information manually each time a call is
placed.
Frequently, to enhance the versatility of such
devices, they are made programmable with individual
devices being programmed to store different telephone
numbers, and/or calling card, credit card or personal
identification numbers (PINS>. While such programming is
generally performed by electronically coupling such
programmable devices to a programming unit, for example,
as described in U.S. Patent No. 4,882,750 to Henderson et
al., it has been suggested that such devices should be
designed to be capable of being programmed by acoustic
signals received from a telephone. For example, PCT
Patent Application Number 02837, now abandoned, suggests
a portable electronic information card capable of being
programmed in response to acoustic signals.
While known portable electronic information
cards and auto-dialers that can be acoustically coupled
to telephone systems facilitate telephone dialing and the
supplying of billing information over the phone, the lack
of a practical workable device which deals with past data
transmission errors and security problems has inhibited
widespread acceptance and use of such auto-dialer
devices.
The introduction of errors into the data being
sent to the telephone system, e.g., as the result of the
ease of an acoustic coupling, is one example of a data
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error problem that may prevent the telephone system from
completing a call. As will be discussed in detail below,
errors associated with the use of an acoustic coupling
result from various factors affecting the acoustical
transmission of DTMF tones. Such factors include
variations between components used in present auto-
dialers to generate the DTMF tones, temperature
variations affecting battery voltages and the
amplification levels applied to DTMF signals, speaker
proximity to a telephone handset's microphone used to
receive the acoustic DTMF tones, distortions introduced
by the microphone receiving DTMF tones output by an auto-
dialer, as well as, ambient noise levels. Errors may
also be introduced from the lines that connect a caller
to the ultimate telephone call destination as well as
from other sources.
In addition to the error problems associated
with the use of known auto-dialers, known devices for
providing calling card and caller identification
information acoustically to a telephone system present
many security problems. For example, an unauthorized
tape recording of a calling card number generated by the
known systems, can easily be created by connecting an
input cable to the telephone cable connected to a coin
phone and then played back by an unauthorized user
seeking to obtain access to the telephone system.
Generally, the known calling card systems fail to provide
a security method for preventing unauthorized users from
gaining access to the telephone system via the use of
such an unauthorized recording. Furthermore, known
systems fail to prevent an unauthorized person from
obtaining a calling card number and its related Personal
Identification Number(PIN), both of which can be
repeatedly used in their identical form for subsequent
calls, through other methods, e.g., video-taping an
authorized caller in a public place, going through the
trash outside of large office facility, etc. Once known,
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calling card number and PIN data can be used to initiate
multitudes of calls, often to foreign countries. The
aggregate cost of the fraudulent use of unauthorized
calling card calls in the United States is estimated to
exceed $1 billion per year. While long distance carriers
are now providing software analysis of many calls placed
on their network to determine if there is a likelihood of
unauthorized use, many such calls are paid by authorized
customers who fail to notice the unauthorized calls on
their bills.
Accordingly, there is a need to provide a
secure device and method for storing and providing
information regarding a user, and, more specifically, for
providing such information locally or transmitting it
remotely by, e.g., calling card, credit card, and user
identification information either through or to a
telephone system.
In addition to the reliability and security
issues discussed above, there are also several
convenience problems associated with known auto-dialer
devices some of which are inherent in the standard credit
card calling transaction illustrated in Fig. 1. These
convenience problems include the need to generate and/or
input separate telephone number and calling card
identification information when attempting to place a
credit card call. Furthermore, the procedures often used
to initiate a calling card call often require that a user
interlace carrier access codes (up to 20 digits) followed
by the user's desired destination number (up to 17
digits) followed by an account/pin # array (usually at
least 14 digits). These input sequences, which may
expand in the future to accommodate greater call/user
volumes are difficult sequences for a user to supply
without input errors, and because of their complexity
often result in users holding a publicly viewable card
showing the account number and dialing sequences needed,
creating security risks from unscrupulous users of
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calling card account and access data.
Additionally, because many countries have a
distinct dialing sequence and numbering plan, carrier
access codes are rarely identical from country to
country, thereby increasing the difficulty that a
traveler experiences when placing a calling card call.
Other convenience problems with the known
devices relate to size and general ease of use issues.
For example, known devices may be of such a size that it
is inconvenient for a user to keep the device with them
throughout the day. In addition, the size and shape of
many of the known auto-dialers makes it difficult to
properly align the auto-dialer with the microphone of a
standard telephone handset making it somewhat difficult
to use if accurate transmission of DTMF signals is to be
achieved. Furthermore, the number of keys and the
complexity of the controls frequently encountered on the
known portable electronic information cards and auto-
dialers have tended to inhibit the known devices from
gaining widespread acceptance.
While the problems described above mainly refer
to the problems arid errors-associated with the initiation
of calling card calls, each of these problems may also
affect access security and convenience in relation to any
telephone based transaction (e. g. credit card purchases
of over the phone, access to secure voice and data
networks, etc.)
Summary of the Present Invention
The present invention provides a communication
device capable of transmitting and receiving data. In
accordance with the present invention, data may be
encoded into a signal comprising a series of tones or
tone pairs, e.g., a conventional DTMF signal, by
controlling various identifiable components or aspects of
the signal, e.g, the amplitude, frequency etc., of lack
tone, or the period between tones. When multiple signals
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are used, e.g., a combined Lo-frequency tone signal and a
Hi- frequency tone signal, the twist, i.e., amplitude
difference between the signals, may also be used to
encode data.
5 In accordance with one embodiment of the
present invention, the signal characteristics described
above are used to encode data into a DTMF signal which is
still detectable by a standard DTMF signal detector. In
this manner, the present invention, permits data to be
10 embedded or encoded into a DTMF signal being used, e.g.,
to place a call. The embedded data may represent, e.g.,
a telephone calling card number, destination telephone
number information or other data.
In one embodiment, the present invention is
implemented as an auto-dialer also suitable for use as a
smart card which is capable of transmitting and receiving
information over conventional telephone lines, e.g.,
between a database and the auto-dialer, without the need
for a specialized interface (other than a standard
telephone). The auto-dialer of the present invention is
capable of being acoustically coupled to the receiver of
a telephone and being reprogrammed in response to
acoustic signals. The programming and other features of
the auto-dialer can be individually enabled or disabled
in response to pre-selected signals, e.g., a string of
DTMF tones received by the auto-dialer. In this manner,
in one embodiment, the auto-dialer of the present
invention requires an acoustic "key" to enable/disable
some functions.
Using the encoding technique described above,
an auto-dialer according to the present invention can
encrypt calling card and other data intc, e.g.,
destination telephone numbers by selectively altering
pre-selected characteristics of a DTMF tone sequence,
such as the duration of tones, the period of silence
between tones and the twist between Lo-band and Hi-band
tones of DTMF tone pairs in the conventional DTMF
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protocol which represent the desired destination
telephone number. In accordance with the present
invention, the encryption of data into the destination
telephone number does not affect the ability of standard
telephone switching equipment to recognize the
destination number. However, information encrypted into
the DTMF signals will be undetectable to standard
telephone switching circuitry because it is encrypted
using DTMF signal characteristics not normally used to
represent data related to conventional call processing.
In one embodiment, other tones or frequencies are also
used to transmit data which cannot be detected by
standard DTMF tone detectors.
In addition to the encryption capability
described above, the auto-dialer of the present
invention, in one embodiment, has a system clock that is
used to drive a pseudo random number generator used in
various data security schemes.
The auto-dialer of the present invention
incorporates various calibration features which permit
the calibration of the audio output and system clock. In
one embodiment calibration adjustments are made by
programming the auto-dialer with various calibration
factors. This programming may be done by an acoustic
coupling device incorporated into the auto-dialer or via
another input device, e.g., wired to the auto-dialer
either at the time of manufacture or over the phone at a
later time. The calibration features permit the easy
calibration of both the system clock and various
characteristics of the tones generated by the auto
dialer.
In addition to the various encoding and
calibration features of the present invention, the
present invention is also directed to a variety of
security schemes and features whic': are designed to
generally increase security when placing a telephone call
and/or when providing other confidential or user-
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identification-related information.
Each of the above described features of the
present invention, as well as numerous other features,
will be described in greater detail below.
Brief Description of the Drawings
Figure 1 is a flow chart illustrating the steps
involved with placing a standard telephone call using a
credit card.
Figure 2 is a schematic block diagram of an
exemplary embodiment of an auto-dialer in accordance with
one embodiment of the present invention.
Figure 3 is a more detailed diagram of the
auto-dialer illustrated in Fig. 2.
Figure 4 is a diagram illustrating DTMF decoder
circuitry suitable for use in the auto-dialer of Figs. 2
and 3.
Figure 5 is a diagram illustrating DTMF encoder
circuitry suitable for use in the auto-dialer of Figs. 2
and 3.
Figure 6 is a flow chart illustrating the steps
associated with the placing of a credit card call using
the auto-dialer of the present invention.
Figure 7 is a block diagram of the auto-dialer
of the present invention being coupled to a destination
telephone via a carrier switching center.
Figure 8A is a chart illustrating the
fundamental difference between the tones of various DTMF
tone pairs generated by standard DTMF generators.
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Figures 8B-8E are charts illustrating the
accept/reject and out-of-range frequencies, of a standard
DTMF detector circuit, in relationship to each of the
four fundamental Lo-band frequencies and four fundamental
Hi-band frequencies used to generate standard DTMF
signals.
Figure SF is a chart illustrating exemplary
output levels of both carbon and electret microphones
when receiving acoustic high-frequency tones associated
with the DTMF tone pair representing the indicated
digits.
Figure SG is a chart illustrating exemplary
output levels of both carbon and electret microphones
when receiving acoustic low-frequency tones associated
with the DTMF tone pairs representing the indicated
digits.
Figure 9A is a chart illustrating the
fundamental difference between the various tone pairs
when the frequency of the Lo-band and Hi-band tones are
selected, in accordance with the present invention, to
reduce third tone errors.
Figure 9B is a chart illustrating twist values
of DTMF tone pairs generated in accordance with one
embodiment of the present invention.
Figure l0A is an illustration of a bottom view
of one embodiment of the auto-dialer of the present
invention.
Figure lOB is an illustration of a top view of
the auto-dialer illustrated in Fig. 10A.
Figure 10: is an illustration a side view of
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the auto-dialer illustrated in Fig. 10A.
Figure lOD is an illustration of a cut away
side view of the auto-dialer illustrated in Fig. 10A.
Figure l0E is an illustration of the auto-
dialer illustrated in Fig. l0A mounted on a key ring.
Figure 11 is a chart illustrating exemplary
signal characteristic values, for a DTMF tone pair
representing the digit 3, that can be used to represent
data in accordance with the present invention.
Figure 12A illustrates an exemplary Lo-band
tone level to data conversion table in accordance with
the present invention.
Figure 12B illustrates an exemplary Hi-band
tone level to data conversion table in accordance with
the present invention.
Figure 12C illustrates an exemplary tone
duration to data conversion table in accordance with the
present invention.
Figure 12D illustrates an exemplary interdigit
period duration to data conversion table in accordance
with the present invention.
Figure 12E illustrates an exemplary Lo-band
tone frequency deviation to data conversion table in
accordance with the present invention.
Figure 12F illustrates an exemplary Hi-band
tone frequency deviation to data conversion table in
accordance with the present invention.
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Figure 12G illustrates an exemplary tone pair
twist level to data conversion table in accordance with
the present invention.
5 Figure 13 illustrates a chart which displays
the data conversion results obtained by using the signal
characteristic values of chart 11 in conjunction with the
conversion tables of Figs 12A through 12G to decode
information encoded into a DTMF tone pair in accordance
10 with the present invention.
Figure 14 is a schematic block diagram of an
access control device implemented in accordance with one
embodiment of the present invention.
Detailed Description
The present invention is directed to methods
and apparatus for communicating data through the use of
acoustic or electrical signals including, e.g., DTMF
signals. Various embodiments of the present invention
are directed to, e.g., portable acoustically coupled
auto-dialers, calling cards, credit cards, paging
devices, smart cards, and other information card type
devices, debit cards, etc. In addition to such portable
embodiments, several embodiments of the present invention
are directed to telephone switching circuitry and DTMF
and other tone recognition circuitry which may be
incorporated into existing telephone systems, as well as
other data systems.
Referring now to Fig. 2 there is illustrated an
auto-dialer device, generally indicated by the reference
numeral 100, in accordance with one exemplary embodiment
of the present invention. As illustrated, the auto-
dialer 100 comprises a microprocessor 104 coupled to a
read only memory (ROM) 106, an input device 105, e.g.,
input keys, a random access memory (RAM) 108. The ROM
may be located within the microprocessor 104 or
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externally thereto.
Via input device 105, the microprocessor 104
receives input signals from a user which input stored in
the RAM 108 or processed by the microprocessor 104 using
other information stored in the ROM 106. In addition, in
various embodiments, the RAM 108 is used to store data
relating to voice signals and/or tone signals.
The auto-dialer 100 further comprises a DTMF
encoder 110 and a DTMF decoder 112 which are coupled to
the microprocessor 104 and to a speaker 114. in the
illustrated embodiment, the speaker 114 serves as both an
input device for receiving acoustic signals, such as DTMF
tones, and as an output device for outputting signals
such as DTMF tones and other signals generated by the
encoder 110. In other embodiments, a separate microphone
is used for receiving audio signals and the speaker 114
is used only for outputting signals.
As illustrated in Fig. 2, the auto-dialer 100
may be acoustically coupled to a standard telephone 122
such as a public pay phone. While the speaker 114 is
illustrated in Fig. 2 as receiving a signal from and
sending a signal to, a telephone handset 121, it is to be
understood that the speaker 114, in this embodiment, can
not be used to perform these operations simultaneously.
Furthermore, it should be noted that when receiving
signals from the handset 121, the speaker 114, which
serves as a transducer, is positioned in close proximity
to the handset's speaker 120 and while sending signals to
the handset's microphone 118 the speaker 114 is
positioned in close proximity to the microphone 118.
Thus, to change between the send and receive functions,
in the illustrated embodiment, a user must move the auto-
dialer 100 from being in close proximity to the
microphone 118 to a position where it is in close
proximity to the speaker 120. However, in another
embodiment, a separate microphone is included for the
receipt of data in addition to the speaker 114. In
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accordance with such an embodiment, data may be received
and transmitted simultaneously by the auto-dialer 100,
without the requirement of moving the auto-dialer 100.
In another embodiment, the auto-dialer 100 is
designed to acoustically monitor its output and perform
an auto-calibration sequence prior to or at the beginning
of, each period of use of the auto-dialer 100 which
follows a period of dormancy of a preselected time
period, e.g., a selected number of hours or days or when
the autodialer 100 senses a temperature outside of a
preselected temperature range, e.g., representing the
temperature the autodialer 100 is expected to work at.
As is well known, battery voltage output varies
as a function of temperature. Variations in voltage
output are particularly noticeable in cold weather:
Additionally, other components of the autodialer 100 are
subject to the effects of temperature. Accordingly, in
one embodiment, the autodialer 100 incorporates an auto-
calibration feature which causes the generation of a
preselected group of tones used for calibration purposes.
As these bones are generated, the microphone 107 receives
the-tones and converts them to electrical signals which
are analyzed by the microprocessor 104. The
microprocessor 104 analyzes the generated signal levels
and compares them against stored desired signal level
values. In the event that an adjustment is required in
any tone output level, or other signal characteristic,
the microprocessor 104 calculates the appropriate change,
and alters a tone generation control parameter stored in
the RAM 108 to correct the output signal level. The
autodialer 100 may then re-test the generation of the
tone which had a tone signal level problem to insure
accurate generation of the tone to insure that the
calculated parameter change produced the desired result.
If the desired output level was not achieved, the
microprocessor repeats the calibration sequence. In one
embodiment, when it is detected that a tone signal level
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fails to achieve the pre-determined level, e.g., desired
signal level after one or more attempts to adjust the
output level, the auto-dialer 100 indicates a "don't use"
condition on a display device 202.
Referring now to Fig. 3, the auto-dialer 100 of
Fig. 1 is illustrated in greater detail. In Fig. 3,
components that are the same or similar to those of Fig.
2, will be referred to using the same reference numerals
as used in Fig. 2. As illustrated in Fig. 3, the auto-
dialer 100 may further comprises the display device 202
for displaying data and other information output by the
microprocessor 104, and/or system components, a main
battery for powering the auto-dialer 100, a back-up
battery 206 for supplying power to the microprocessor 104
as well as other system components, when the main battery
fails, and a voltage comparator 210 for detecting the
condition of the main and backup batteries 206, 208.
As illustrated in Fig. 3, the auto-dialer
further includes a micro-power amplifier 226 coupled to
the output of the speaker 114. The amplifier 226 serves
to provide a wake-up signal to the microprocessor 104 as
described below. The amplifier 226 generates a signal in
response to a signal generated by the speaker 114 in
response to received acoustic signals. The signal output
by the amplifier 226 causes the microprocessor 104 to
become fully active from, e.g., a sleep mode which is
automatically entered into after a long period of
inactivity in order to conserve power. In an alternative
embodiment, an input of the microprocessor 104 is coupled
to a light sensor or other activation device such as a
radio frequency sensor, which causes the auto-dialer 100
to become fully active in response to an outside stimulus
which may be provided by, e.g., a light or sound source
associated with an automatic teller machine (ATM) or
telephone device. Thus, in accordance with such an
embodiment the auto- dialer 100 can be made active by the
excitation of a transducer or other sensor, by, e.g., a
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light, radio frequency signal or the receipt of an
acoustic signal having a pre-defined frequency and a
minimum, pre-defined intensity level. These pre-defined
levels or values are a matter of design choice and may be
programmed into the ROM 106 or RAM 108 at, e.g., the time
of manufacture.
With regard to "wake-up" features, in one
embodiment, the auto-dialer 100 incorporates a reflective
surface, e.g., a reflective ring 106 as illustrated in
Fig. l0A or other component which can be detected by an
interface of e.g., an ATM machine. For example, an ATM
machine may detect the presence of the auto-dialer 100
because of its unique shape when it is place in contact
with the ATM machine. As will be discussed below, with
regard to Fig. 10A, the auto-dialer 100 may include a
notch or cut out designed to mate with the shape of the
input area of the interface with which the auto-dialer
100 is intended to communicate. Because of the auto-
dialer's reflective surface 106 shape, or other physical
characteristic, the interface of the machine with which
the auto=dialer 100 is designed to communicate can detect
the presence of the auto-dialer 100 and signal the auto-
dialer through, e.g., a series of tones, to become
active, e.g., "wake-up". Accordingly, the auto-dialer
100 permits interfacing hardware to recognize the
presence of the autodialer 100 by, e.g., the presence of
a highly reflective material, e.g., a mirrored film or
other similar material, which reflects an emitted light
from the interfacing hardware in such a fashion as to
cause a light detecting sensor in the interfacing
hardware to sense the reflection of such light, and upon
the sensation of such light, cause the interfacing
hardware to emit a pre-determined set of tones which will
cause the autodialer 100 to become active and enter a
mode of operation which may not otherwise be available to
the user.
The microprocessor's ROM 106 includes a series
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of memory locations which contain information that serves
as a set of permanent data tables, as well as a computer
program instructions for controlling the operation of the
microprocessor 104. The permanent data tables may
5 contain e.g., long distance carrier information, area
code information data encoding/decoding information,
and/or credit service related information as will be
described further below.
The RAM 108, on the other hand, is used to
10 store information that is device dependent, is likely to
change, or for other reasons more easily stored in an
alterable memory device than a ROM. As illustrated by
the representative memory map 211, the RAM 108 may
dedicate memory space to storing DTMF transfer and
15 receive parameters 214 used for encoding/decoding
signals, information 216, e.g., frequency information
relating to supported tone pairs, display memory 218,
system control data, e.g., calibration parameters 224,
user data 222, (e.g., destination phone numbers and
20 billing information relating to the individual who is
authorized to use the auto-dialer 100) and device data
222, (e. g., one or more numeric or alpha-numeric
sequences which identify the particular auto-dialer 100,
manufacturing date information, etc.)
A circuit suitable for use as the DTMF decoder
circuit 112 illustrated in Figs. 1 and 2 will now be
described with reference to the schematic block diagram
of Figure 4. As illustrated in Fig. 4, the DTMF decoder
circuit 112 comprises an amplifier and filter circuit 302
that has an input coupled to the output of the speaker
114 and a received signal output coupled to the input of
a Hi-band passband filter 304 and a Lo-band passband
filter 306. In this embodiment, the speaker 114 acts as
an inductor converting acoustic signals received from,
e.g., the speaker 120 of the telephone handset 121 into
electrical signals which are amplified and filtered by
the circuit 302 and then further filtered by the passband
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21
filters 304, 306. The Hi-band passband filter 304, is
designed to pass the corresponding Hi-band frequency DTMF
signals while eliminating noise and other signals.
Similarly, the Lo-band filter 306 is designed to pass the
Lo-band frequency DTMF signals and to eliminate other
signals. In this manner, the Lo-band and Hi-band signals
are segregated from each other with noise, i.e., signals
having frequencies outside the bands of the DTMF signals)
being removed to facilitate the later decoding of the
signals.
An output of the Hi-band filter 304 is coupled
to the input of a column frequency detector 208 for
detecting which frequency of the set of Hi-band tone
frequencies is being received. Similarly, the Lo-band
filter 306 has an output coupled to an input of a row
frequency detector 310 for detecting which frequency of
the set of Lo-band frequencies is being received. In
particular embodiments, the column and row frequency
detectors 308, 310 as well as Hi and Lo band filters 304,
306 may be designed to recognize and pass additional Hi-
band and Lo-band tones, respectively, which are outside
the range of standard DTMF-tones to thus increase the
number of signals which can be used to transmit data to
add additional security, increase data transmission
rates, or provide additional features.
An output of the column frequency detector 306
and an output of the row frequency detector-310 are
coupled to corresponding inputs of a DTMF signal detector
312. The DTMF signal detector 312 receives the Lo-band
and Hi-band tones output by the column and row frequency
detectors 308, 310 along with information signals
indicating the frequency of the received tones. The DTMF
detector 312 determines if the received tones constitute
a valid tone pair or other signal which the DTMF signal
detector 312 is programmed to recognize. If the DTMF
signal detector 312 detects a valid tone pair or a signal
it recognizes, it sends a signal to a tone to data
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22
converter 316 circuit of the microprocessor 104 to
convert the detected DTMF tone or signal into the data it
represents, e.g., a symbol or number.
Because the auto-dialer 100 is programmable, it
may be programmed or reprogrammed to accept one or more
signals as valid tones. These tones may include tones
other than those used for standard DTMF signals.
Furthermore, it can be programmed to reject or ignore
input data which does not conform to predetermined signal
characteristics which are stored in the RAM 108 of the
auto-dialer 100. In one embodiment, these signal
characteristics (e.g. maximum tone-length) may be
remotely modified via, the acoustic reprogramming of the
auto-dialer 100 in response to the auto-dialer 100
receiving a series of DTMF tones. Such tones act as a
signal or key which is required to enable the
reprogramming of the auto-dialer 100. In addition,
because the auto-dialer 100 is designed to be both
responsive to, and capable of, generating audio tones,
e.g., both standard and encoded DTMF tones, as will be
described below, the auto-dialer 100 is capable of
receiving, storing and transmitting both standard and
encoded DTMF tones for a variety of purposes including
for use as passwords and "keys" to enable certain
functions of the auto-dialer 100 or the device which the
auto-dialer 100 is used to communicate with.
In yet another embodiment, the auto-dialer 100
is programmed to, upon the receipt of pre-selected series
or group of tones, representing commands or instructions
to the microprocessor 104, perform mathematical
computations based on either data stored within the auto-
dialer 100 and/or on data which is received by the auto-
dialer 100 in response to the received commands. In such
an embodiment, the performed computations) is in
accordance with a received instruction and is performed
in such a manner that a user can not effect the result of
the computation by manipulating the keys on the auto-
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dialer 100. In this manner, the auto-dialer 100, because
of its programming and ability to receive commands and
data from an outside source, can perform, e.g.,
debit/credit calculations with the user being unable to
manipulate the result from the input device 105 of the
auto-dialer 100. Additional security features to prevent
unauthorized manipulation of data stored in various
locations within the memory 106, 108 of the auto-dialer
100 will be discussed below.
As discussed above, for security reasons, the
reprogramming feature is, in some embodiments, enabled
only upon the receipt of a pre-selected group of acoustic
tones which serve as a key to indicate to the auto-dialer
100 that an authorized individual is in fact
reprogramming the device. Different acoustic keys or
tone sequences may be used to limit access to different
memory locations. In this manner, one key, e.g., a
series of tones, may be required to reprogram one memory
location while another key may be required to reprogram
another memory location. In this manner, the ability to
alter the contents of various memory locations
containing, e.g., personal identification telephone
numbers, prefix information, etc. can be restricted so
that the user cannot change the contents of certain
memory locations and so that only services authorized to
alter particular items in memory, e.g., dialing prefixes,
country codes, etc. can alter such information. In such
an embodiment, a first series of tones is required to
alter the contents of a first memory location while a
second series of tones is required to alter a second
memory location. Additional tone sequences or "keys" may
be associated with additional memory locations.
In one embodiment, the DTMF signal detector 312
of the present invention referred to as an enhanced DTMF
signal detector is able to monitor alterable
characteristics o~ x DTMF signal, e.g., signal twist, Lo-
band and Hi-band tone amplitude, Lo-band and Hi-band tone
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24
duration, tone frequency, etc. which may be used to
encode information into a DTMF signal without affecting
the ability of a standard DTMF signal detector to detect
the symbol/number represented by a DTMF tone pair. If
the DTMF signal detector 312 detects encoded information
the encoded information is supplied to the DTMF tone to
data converter 316 for processing. A particular signal
or sequence of tones is used in some embodiments to
provide an indicator signal to indicate to a receiver
that encoded DTMF signals are being transmitted. In such
embodiments, a DTMF signal detector detects the receipt
of encoded DTMF signals by monitoring a received signal
for such an indicator signal or indicator sequence of
tones.
The DTMF signal detector 312 also has start and
stop signal outputs coupled to corresponding inputs of a
non-tone demodulation circuit 314 of the microprocessor
104. In this manner, the non-tone demodulation circuit
314 receives timing information concerning the starting
and stopping of each received signal. As will be
discussed below, this inforniation can be used, in
accordance with one embodiment of the present invention,
for decoding information encoded into one or more DTMF
signals and/or for distinguishing of a string of signals
which represent meaningful data as opposed to nonsense
signals added for security reasons as well as to enable
the device to provide non-frequency dependent data that
is encoded into the interdigit periods, i.e., the time
between DTMF tone pairs.
Referring now to Fig. 5, the microprocessor 104
and a DTMF encoder circuit 400, which may be used as the
DTMF encoder 110 illustrated in Fig. 2, will now be
described in detail. The DTMF encoder 400 comprises a
high frequency register 424, a tone select register 426,
and a low frequency register 428.
The high and low frequency registers 424, 428
have a first input coupled to a data output of the
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microprocessor 104, a second input coupled to a tone
select output of the microprocessor 104 and a third input
coupled to a tone select signal output of the tone select
register 426.
5 The tone select register 426 receives tone
signal information from a tone store output of the
microprocessor 104 which is then processed to generate a
control signal which is supplied to the low and high
frequency registers 424, 428 through the third input of
10 the registers 424, 428.
The high and low frequency registers 424, 428
are responsive to signals received from the
microprocessor 104 and the tone select register 426 to
produce a control signal indicating the fraction of the
15 microprocessor's clock frequency the desired Hi and Lo
tones correspond to.
The Hi-band DTMF tone of each DTMF tone signal
pair is generated by a Hi-band frequency signal
generation circuit 401. The Hi-band frequency signal
20 generation circuit 401 comprises a programmable divider
430, which is coupled to a Johnson counter 434. The
Johnson counter 434 is coupled to digital to analog
converter 438 which has an output coupled to an amplifier
458 which is responsible for amplifying the Hi-band DTMF
25 tone signals of each tone pair.
The programmable divider 430 receives as input
signals the output of the high frequency register 424 and
the microprocessor's oscillator. Using the control
information provided by the high frequency register 424,
the programmable divider generates a digital signal
having the desired frequency of the Hi-band tone to be
generated from the oscillator signal. This digital
signal is then further processed by the Johnson counter
434 before being converted into an analog signal by the
D/A converter 438.
It should be noted that to avoid the problems
that may result from harmonics associated with
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26
squarewaves, the D/A converter 438 only generates pure
sine waves. The analog Hi-tone output signal, output of
the D/A converter 438, is amplified by the amplifier 458
which has a gain control input coupled to a Hi-band
amplitude control signal output of the microprocessor
104.
As will be discussed below, the degree of
amplification performed by the amplifier 458 is
controlled by the microprocessor 104. In this manner,
the microprocessor 104 can introduce intentional twist
into the DTMF signal being generated and/or encode
information into the DTMF signal by selectively varying
signal strength and/or twist associated with the tone
pairs comprising the DTMF signal being generated.
A Lo-band frequency signal generation circuit
480 comprising a programmable divider 432, a Johnson
counter 436, a (D/A) digital to analog converter 440, and
an amplifier 480 is responsive to the output of the low
frequency register 428, the microprocessor's oscillator,
and the microprocessor's Lo-band amplitude control
signal, to generate the Lo-band DTMF tone in the same
manner as described above with regard to the generation
of Hi-band DTMF tones.
The output of each of the amplifiers 458 and
460 which comprise the Hi-band and Lo-band tones,
respectively, of each DTMF tone pair being generated, are
supplied to first and second inputs of a dual ported
amplifier 452 for additional amplification. The
amplifier 452 has a control input which is coupled to a
timing control output of the microprocessor 104.
The timing control signal is used to control
the amount or level of amplification the amplifier 452
provides. In addition, by asserting the timing control
signal the microprocessor 104 enables the amplifier 452
during periods of data transmissior_. On the other hand,
when the speaker 114, which has an input coupled to the
output of the amplifier 452, is being used as a receiving
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device or microphone, the microprocessor 104 de-asserts
the timing control signal thereby deactivating the
amplifier 452 and thus the output of the DTMF tone
encoder 400. The timing control signal may also be used
to inhibit signal output during the interdigit periods.
Various features of the present invention,
directed to overcoming the data error, security and
convenience problems associated with known auto-dialer
devices will now be described with reference to the auto-
dialer 100.
Each feature of the present invention will be
discussed in detail below beginning with a discussion of
the features of the present invention which are directed
to reducing the error rate associated with the acoustic
transmission of information represented by DTMF signal
tones, e.g., telephone number and credit card number
information, from the auto-dialer 100 of the present
invention to a DTMF signal receiver such as a telephone
handset 120. This particular feature of the present
invention may be described as an error avoidance feature.
I. Error Avoidance Features
In accordance with the present invention,
several methods are used to avoid or compensate for the
occurrence of errors commonly associated with the
acoustic transmission of a DTMF signal to a standard
telephone system, e.g., a handset. These methods are
directed to eliminating, or compensating for, common
sources of errors that are associated with acoustic
transmission of a DTMF signal. The methods of error
avoidance of the present invention will generally be
discussed according to the source of the error and the
particular method of the present invention directed to
eliminating or compensating for such error sources.
A. Third Tone Errors
One of the most common sources of errors
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28
associated with known acoustically coupled auto-dialers
is generally referred to as the "third tone" problem.
This problem is, as the name suggests, associated with
the detection of a third, otherwise valid tone, at the
detector stage of a receiver where a DTMF tone signal is
being decoded. As described above, a DTMF tone signal is
only considered valid if it includes a single pair of
valid tones, i.e., one valid Hi-band tone and one valid
Lo-band tone. Thus, when multiple valid Hi-band or Lo-
band tones are received at the same time, the DTMF signal
is considered invalid and can not be properly decoded.
The relative amplitude of a received tone compared to the
other received tones may, in some cases, be used to
distinguish valid tones from erroneous invalid tones.
when used as collectors of DTMF tones, carbon
based microphones, which are commonly used in standard
telephone handsets because of their low cost and high
degree of reliability often generate and transmit
erroneous tones, e.g., third tones, in addition to the
tones actually received by the microphone. Such errant
third tones can cause errors in some tone detection
receivers, and particularly those systems which do not
utilize digital signal processing equipment for tone
detection.
The transmission of DTMF tone signals through
carbon microphones causes the carbon granules within the
carbon microphone to vibrate in relation to the driving
frequencies. As a result of the harmonic effect of the
varying vibrations of the granules, various residual
tones are generated, with the third tone being the most
powerful of these residual tones. This third tone can be
relatively powerful, e.g. as much as one half the power
level of the higher of the two received acoustic DTMF
tones passing through the microphone. The frequency of
this third tone, will normally be the arithmetic
difference between the frequencies of Hi-band and Lo-band
tones being received by the carbon microphone.
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Referring now to Fig. 8, there is illustrated a
chart with four columns. In the chart 9, the number or
symbol in the first column 11 represents those numbers or
symbols available on a standard telephone keypad. The
second column 13 represents the Lo-band frequency
associated with the corresponding number or symbol in the
first column 11 while the third column 15 represents the
corresponding Hi-band frequency. The fourth column 17
represents the fundamental difference between the Lo-band
and Hi-band frequencies listed in columns two and three
13, 15. It is this fundamental difference frequency that
represents the frequency of the third tone that is
generated by a carbon microphone when the corresponding
Lo-band and Hi-band frequencies are received. As will be
discussed further below, the fundamental difference
frequency, or third tone frequency associated with the
symbols/numbers 3, 6, a, b, c, and d will fall within
the passband of the filters of many standard DTMF
detectors.
The third tone error problem is particularly
significant with regard to the tone pairs representing
the numbers symbols 3, 6, a, b, c, and d because, in
their case, the third tone created from the harmonic
effect associated with the carbon microphone falls within
the tolerance range of the low frequency band tones and
the band pass filters corresponding to these frequencies.
Thus, in the case of these numbers and symbo3s, the third
tone signal will fall within the passband of the filters
of many standard DTMF detectors and will therefore not be
filtered out.
As discussed above, the presence of such an
errant tone within the frequency range of valid tones,
may cause a detector to detect two valid Lo-band tones,
when only one should be present. While the level of the
deliberately generated tone will normally be much higher
than the errant signal tone, without the use of digital
signal processing which is able to select the tone with
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the higher power level, a detector will have difficulty
in determining which of the two Lo-tones received should
be used. Normally, when the DTMF detector is unable to
select the valid or deliberate tone from the two Lo-band
5 tones, the DTMF tone detector will ignore the tone-pair
signal which includes the third tone , causing the entire
dialed string to be lacking the errant digit and, thus,
preventing the connection of the call or the completion
of a data string being used for other purposes.
10 While the third tone will not always be of such
an intensity that it results in an error, and while
digital signal processing in DTMF detectors is becoming
more common, for an acoustically coupled auto-dialer 100
to offer maximum versatility it must be capable of
15 transmitting telephone and credit card number information
accurately to the vast majority of existing telephone
systems including those that do not perform such digital
signal processing. Accordingly, the third tone problem
associated with carbon microphones needs to be reduced or
20 compensated for to increase the reliability of
acoustically coupled auto-dialers if such auto-dialers
are to work reliably with the vast majority of existing
telephone systems.
The present invention, addresses the third tone
25 problem in two ways. The first approach is directed to
avoiding using symbols/numbers which are likely to
produce third tone errors. On the other hand, the second
approach is directed to altering the nominal frequency of
the tones which are likely to generate third tone errors
30 in an attempt to avoid such errors.
i. Avoidance Of The Use OF Symbols/Numbers
Likely To Produce Third Tone Error
Problems
As discussed above, the first approach of the
present invention to dealing with the third tone problem
revolves around avoiding the use of numbers/symbols that
are most likely to produce the problem in the first
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place. i.e., the numbers/symbols 3, 6, a, b, c, and d.
Because most credit card, calling card, and telephone
numbers use only the digits 0 9 found on standard, non-
extended keypads such as those found on pay phones, most
third tone problems can be eliminated by merely avoiding
the use of the numbers 3 and 6.
Thus, in accordance with one embodiment of the
present invention, when assigning numbers, e.g.,
telephone numbers which must be used to obtain
connection, e.g., via a local telephone switching office
which may not contain digital signal processing
equipment, to a central office, only the digits 0, 1, 2,
4, 5, 7, 8, and 9 are used. In this manner, third tone
problems associated with the numbers/symbols 3, 6, a, b,
c, and d are avoided when sending information to
telephone switching offices which may not have digital
signal processing equipment capable of distinguishing the
actual tone from the undesired third tone signal.
Once a connection has been made to a telephone
switching network with digital signal processing
equipment, such as the type currently found in most long
distance carrier telephone switching offices, the risk of
errors due to third tone problems will be greatly
reduced. Thus, all digits may be used including 3, 6, a,
b, c, and d once a connection has been established to a
system known to include digital signal processing
equipment. Accordingly, the primary time for avoiding
the digits associated with third tone problems is when
establishing connections to local offices or other
telephone switching networks which may not contain the
digital signal processing circuitry required to avoid
third tone problems.
By avoiding the use of the numbers/symbols 3,6,
a, b, c, and d in the above described manner, the vast
majority of third tone problems can be avoided without
the need for digital signal processing circuitry in a
DTMF detector and without modifying the DTMF signal
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32
generator.
ii. Generation Of Tone Pairs Wherein The
Arithmetic Difference of the Generated
Tones Comprising Each Tone Pair Will Fall
Outside The Range Of The Handpass Filters
Included In Standard DTMF Detectors
The second approach of the present invention to
avoiding third tone error problems involves the
generation of tone pairs wherein the arithmetic
difference between the generated tones comprising each
tone pair will fall outside the range of the bandpass
filters included in standard DTMF generators.
Because of manufacturing tolerances and
component differences, DTMF generators will vary slightly
in output frequency from one DTMF signal generator to
another even though the nominal frequencies, which
represent the frequencies the DTMF generators are
designed to produce, will normally be the same. Thus,
DTMF detectors are designed to detect, i.e., accept as
valid, a range of frequencies corresponding to the Lo-
band and Hi-band DTMF tone frequencies.
Referring now to Fig. 8A, there is illustrated
a chart of the frequency accept range of a standard DTMF
detector circuit. As illustrated, the accept range is ~
1.50 + 2 Hz of the nominal frequency illustrated in the
center column of the chart shown in Fig. SB. Referring
now to Fig. 8C there is illustrated a chart of the
frequency reject range of a standard DTMF detector
circuit. As illustrated, the reject range is ~ 3.5% of
the nominal frequency illustrated in the center column of
Fig. 8C. Referring now to Fig. 8D, there is illustrated
a chart of the out of range frequencies of a standard
DTMF detector circuit. These frequencies represent
frequencies outside the accept/reject ranges of a
standard DTMF detector which cannot be recognized by a
standard DTMF detector circuit in a reliable manner.
Referring now to Fig. 8E, there is illustrated a
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composite chart of standard DTMF tone detector circuit
reject and accept ranges. In particular, the chart of
Fig. 8E illustrates the standard accept/reject ranges
associated with each of the eight nominal tone
frequencies listed in the center column of the chart.
Because the Lo-band and Hi-band tones which
will be accepted by a DTMF detector are permitted to vary
over a limited range, e.g., as illustrated in the charts
of Figs. 8A-8E, it is possible to control the generation
of Lo-band and Hi-band tones so that acceptable tones are
generated while the arithmetic difference between the
tones of any generated tone pair will be such that it
will fall outside the accept range of a standard DTMF
detector.
This may be done, by, e.g., providing the DTMF
tone generator which produces tones having a nominal
frequency that is closer to the outside limits of the
acceptable frequency range of those symbols/numbers that
cause third tone problems. For example in one embodiment
of the auto-dialer 100 is designed to generate Lo-band
frequency and Hi-band frequency tones, for the tone pairs
representing, e.g., the digits 3 and 6, that will fall
within a standard DTMF detector's accept range, e.g., the
accept range of a MITELTM model number MT8870D DTMF
detector circuit, but will have an arithmetic difference
that falls outside the detector's accept range. This can
be achieved by selecting the nominal center frequencies
of the DTMF tones generated by the auto-dialer 100 of the
present invention, for the tones used to represent the
numbers 3 and 6, towards the outer edge of the "accept
range" of standard DTMF detector circuits. It should be
noted that in accordance with the present invention, the
microprocessor 104 can be programmed to select and
control the generation of DTMF tones of various tone
pairs, so that the tones of a tone pair will fall within
the accept range oL conventional detectors, but create an
arithmetic difference which is outside the tolerance
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range of such detectors.
Referring now to Fig. 9A, there is illustrated
a chart indicating the Lo-band frequency and Hi-band
frequency of the tones which the auto-dialer 100, in
accordance with one embodiment is programmed to generate,
for each of the listed tone pairs. As will be noted, the
values in Fig. 9A vary from those of Fig. 8A as the
result of the intentional use of tones which will produce
valid DTMF tone pairs while avoiding third tone problems
by generating fundamental differences between the Hi and
Lo tones that will fall outside the frequency accept
range of most DTMF signal detectors.
The significance of the fundamental frequency
differences is particularly significant in light of the
relative power of the third tone noise (margin) which
accompanies the digits 3, 6, a, b, c, d. These noise
levels approach the lower acceptable limits of standard
detectors, and can, because of their frequency, be
interpreted by the detectors as being considered valid
tones, thus providing the detector with two Lo tone
frequencies to decode.
While the generation of tones towards the outer
limits of the acceptable frequency ranges in accordance
with the present invention offers a method of reducing
third tone problems, it also requires that the DTMF
generator of the present invention be more accurate and
stable than would otherwise be required to insure that
the tone generator only produces DTMF tones that will
fall within the acceptance range of a standard DTMF
detector circuit. As will be discussed below,
calibration features of the present invention help insure
that the required accuracy in frequency output is
achieved.
In accordance with the second approach to
reducing third tone problems, the third tones generated
by a carbon microphone will not be interpreted as valid
Lo-frequency tones because of their frequency. In this
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manner, third tone problems are substantially reduced
without the need for the DTMF detector circuitry to
include digital signal processing circuitry.
It should be noted that while this approach
5 provides a suitable method for eliminating or reducing
third tone problems, it requires the auto-dialer 100 of
the present invention to generate DTMF tones with a
higher degree of accuracy then would otherwise be
required. In a device that is designed to incorporate
10 automatic calibration features, such as the auto-dialer
100 of the present invention, it may be possible to
achieve the required higher standards at little or no
additional cost.
15 B. Amplitude Variation Between Low-band And Hi-
Band Frequencies Errors
In addition to errors caused by the presence of
a third tone, errors may also be caused by power
20 differences between the Lo-band and the Hi-band tone
signals comprising a tone pair. These differences depend
largely on the type of microphone used. Referring now to
Figs. 8F and 8G which are charts illustrating exemplary
output levels of both carbon and electric microphone, for
25 the high-tones and low-tones, respective, it can be seen
that for the carbon microphone in particular, there are
significant differences between Hi-band tone signal power
output levels and Lo-band and tone signal output levels
of many DTMF tone pairs. This difference in signal
30 output levels results in the introduction of twist into
the received signal. As can be seen; the twist which
represents distortion, that is introduced by carbon
microphones can be significant.
As discussed above, each of the numbers/symbols
35 of a standard telephone keypad is represented by a DTMF
tone signal, i.e., a tone pair, comprising one Lo-band
tone and one Hi-band tone. Furthermore, for such a
signal to be detected as a valid signal, the difference,
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36
referred to as twist, in the power level between the Hi-
band and Lo-band tone signals of any particular received
tone pair must fall within a specific range for the
signal to be considered valid. The acceptable range of
power levels received by standard DTMF receivers in a
tone pair requires that the Hi-band tone signal power
level is not greater than 4 dHm more or 8 dHm less than
the Lo-band tone signal power level. If these power
level conditions are not met, a received tone pair will
be rejected.
It has been found that carbon microphones tend
to be less efficient at converting low frequency sound
waves, e.g., acoustic Lo-band frequency tones, into
electrical signals then they are at converting high
frequency sound waves, e.g., acoustic Hi-band frequency
tones, into electrical signals. This disparity in
conversion efficiency introduces twist or power level
differences into received tone pairs with a predictable
bias generally in favor of the Hi-band tone signal.
This introduced twist, resulting from the use
of carbon microphones, adds to any twist that may exist
in a tone pair signal generated by an auto-dialer.
While, in some cases the twist introduced by a carbon
microphone may act to counter twist existing in a
received tone pair, in other cases it will simply added
to the degree of twist. In such a case, it may cause a
tone pair which would otherwise have an acceptable degree
of twist to be rejected because of the twist introduced
by the use of a carbon microphone.
Because the vast majority of public telephones
presently in use include carbon microphones (due to their
relative ruggedness and low cost), the twist introduced
by such microphones presents a potentially significant
source of errors for the acoustic transmission of DTMF
signals to telephone systems.
To counter this problem, .:. one embodiment of
the present invention, the Lo-band and Hi-band tone
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37
signals are amplified separately before being supplied to
the audio output device, e.g., speaker. In such an
embodiment, microprocessor 104 controls the independent
amplification of the Lo-band and Hi-band tones via the
amplitude control signals supplied the amplifiers 458,
460 with the Lo-band tones being amplified to a greater
extent than the Hi-band tones. The difference in
amplification is of such a degree that the auto-dialer
100 is designed to compensate for the varying efficiency
of carbon microphones in converting acoustic tone signals
of different frequencies into electrical signals.
Accordingly by intentionally introducing twist
into the tone pairs, e.g., by the separate amplification
of each individual tone in a tone pair being generated by
the auto-dialer 100 of the present invention, it is
possible to counter the predictable non-linear signal
conversion caused by the use of carbon microphones.
In a sense, this approach to error avoidance
may be thought of as introducing intentional distortion
into the relative power levels of a DTMF tone pair to
compensate for the distortion expected to be introduced
into the signal upon reception by a carbon microphone.
While the twist introduced by the use of carbon
microphones is somewhat predictable, twist introduced by,
e.g., line loss introduced by lines coupling the DTMF
signal receiver to the microphone receiving acoustic DTMF
signals from the auto-dialer 100 are somewhat less
predictable. As the result of empirical field tests
conducted using a variety of telephones, it has been
found that the introduction of certain twist values into
a DTMF signal will generally produce better tone
recognition then will be achieved without the
introduction of twist. The varying amplification of Lo-
band and Hi-band tones in the tone pairs being generated
is to cause the electrical signal leaving the receiving
telephone instrument to be in accordance with industry
standards established for optimum performance after the
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conversion of the received signals into electrical
signals.
The amplification of the low tone at a higher
gain level than that of the high tone will also tend to
S cause any resulting third tone to be of a lower level
than that which would be achieved by amplifying both
signals at a higher rate.
Referring now to Fig. 9 there is illustrated a
chart which shows twist values for each of the 16 DTMF
tone pairs normally used for telephone dialing which have
shown to produce satisfactory results under a wide range
of field conditions, e.g. both urban and rural telephone
conditions.
While Figure 9 does not include the extended
character set (a,b,c,d), it should be noted that these
tone-pairs are not included on standard dialing pads and,
therefore, are not recognized by common switching systems
for the placement of calls. The use of these digits is
generally limited to post-access data collection where
one can be reasonably certain that digital processing
equipment will be available to decode such tones,
including their otherwise errant third tones.
While, as described above, it is often
desirable to intentionally vary the level of
amplification of each tone of a tone pair, the amount of
amplification intentionally introduced should be small
enough so that the maximum twist detected by a standard
receiving DTMF decoder will be such that the Hi tone
level is not greater than 4 dB or 8 dB less than the Lo
tone, i.e., such that the twist falls within the range of
what is defined as a standard valid DTMF signal. Since
different telephone microphones (e. g. carbon, electric)
will transmit Hi and Lo tones with varying efficiency,
because line losses can vary significantly, and because
varying speakers will have different spectral output
curves, the determination of optimum twist levels should
be based on field tests including the generation of a
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39
plurality of twist levels, in conjunction with the use of
level detection equipment at a central receiving site to
determine optimum twist levels for a particular device or
type of speaker that will provide for the accurate
detection of the tones by a wide variety of telephones
under varying conditions.
Referring now briefly to Fig. 9, audio output
signal levels and twist levels which have provided
satisfactory results for the indicated tone pairs are
illustrated. As can be seen from the chart in Fig. 9,
the introduction of twist levels of between -8 and +2
dbm, e.g., through the separate amplification of the Lo-
and Hi tones, has provided satisfactory results.
Referring now to Fig. 9C acoustic output levels
of Hi and Lo tones corresponding to the digits 0-9 are
shown. As illustrated, in order to compensate for e.g.,
the uneven energy conversion of Lo and Hi acoustic tones
into electrical signals by carbon microphones, it is
desirable to generate Lo and Hi tones having different
acoustic sound pressure levels. As illustrated, by
varying th.e sound pressure levels by as much as much as 9
dH (SPL), e.g., for the Lo and Hi tones corresponding to
the digit 1 has proven to provide satisfactory results.
It has been found that when testing to
determine the twist levels that are appropriate to be
used with a device, the determination should be based on
the signal characteristics received following
transmission through the public telephone network or
those received at the line end of one of more telephone
instruments, and not simply the characteristics of
locally generated/received signals.
As discussed above, the auto-dialer 100
includes separate Hi-band and Lo-band frequency signal
generation circuits 401, 403 for independently amplifying
both fundamental frequencies of a DTMF tone pair. This
amplification of individual Lo-band and Hi-band tones may
be done to pre-established, e.g., pre-programmed, and
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remotely alterable levels for any selected tone-pair. In
addition, the autodialer's processor 104 and RAM 108 can
be used to store and modify parameters used to control
amplification levels for each fundamental frequency,
5 i.e., tone, of a tone-pair. As discussed further below
with regard to security features of the present
invention, the ability to reprogram or modify the stored
amplification values may be enabled or disabled in
response to the receipt by the auto-dialer 100 of a pre-
10 selected group of tones which can serve as an access key,
instruction or reprogramming command.
Just as the amplification levels of the DTMF
signal, e.g., tone pairs generated by the auto-dialer
100, can be controlled by stored values or parameters,
15 the auto-dialer 100 can adjust the levels of
amplification which are applied to signals received by
the autodialer's audio transducer, e.g., speaker 114. In
addition, the stored information for controlling
amplification levels may be reprogrammed in response to
20 signals received by the auto-dialer 100 with the
reprogramming feature being enabled/disabled in response
to the receipt of a pre-selected series or group of tones
that may be stored in the RAM 108.
25 C. Errors Resulting From Insufficient Signal Power
In addition to third tones and excessive twist,
errors may also result from insufficient signal strength,
i.e., power, at the microphone of the receiver. As
discussed above, one of the conditions for a tone pair
30 signal being interpreted as a valid DTMF signal is that
each tone in the tone pair received at the DTMF detector
have a signal power level that falls within the range of
0 to -25 dBm.
As a practical matter, the minimum sound
35 pressure level of an acoustically coupled and generated
tone that will be recognized by a standard DTMF detector
is a function of the distance of the tone source, e.g.,
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audio output device 114 of the auto-dialer 100, to the
inductor, e.g., microphone 118 of a receiving device. In
addition, the power level of the received signal will
depend on the energy of the signal output by the auto -
dialer 100, the directionality of the sound waves, and
any apparatus provided to focus the sound waves towards
the microphone. Because of these factors, the movement
of the audio output device 114, of the auto-dialer 100
away from a microphone during detonation, i.e., output of
the tones being generated, can result in a sufficient
decrease in the power level of the signal received at the
microphone 116 to cause a tone-pair to be rejected.
The present invention is designed to insure
that the audio signal received at the microphone 116 of a
telephone 122 has sufficient acoustical power that the
electrical signal produced therefrom will be detectable
as a valid DTMF tone signal.
In one embodiment of the present invention, a
proximity sensor 228, such as a pressure switch or light
sensor, is incorporated into the audio dialer 100 of the
present invention to detect the auto-dialer's proximity
to a telephone microphone 116. In such an embodiment,
when the autodialer's speaker 114 is placed in close
proximity to the microphone 116, the tone signal output
of the auto-dialer 100 is enabled. In the event that a
user moves the auto-dialer away from the microphone 116,
as indicated by the output of the proximity sensor 228
and detected by the microprocessor 104, the auto-dialer
100 will prevent or cease the output of DTMF tones and
indicate, e.g., through the use of a user - noticeable
signal, e.g., an audible signal or a message on the
display of the auto-dialer 100, that the auto-dialer 100
should be placed closer to the microphone 116. Such a
light output may be incorporated into the display device
202.
In this manner, tones will be generated only
when the speaker 114 of the auto-dialer 100 is in close
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enough proximity to the microphone 116 to prevent or
limit the number of errors that might otherwise occur due
to lower or varying tone characteristics due to a varying
or excessive distance between the output of the auto-
s dialer 100 and the corresponding microphone 116 resulting
from a user moving the auto-dialer 100 away from the
microphone 116 while tones are being generated.
As discussed above, in order to insure that a
user keeps the auto-dialer 100 in close proximity to the
microphone of a receiver when pulsing out tones, in one
embodiment, as illustrated in Fig. 3, the auto-dialer 100
also includes an audio and/or visual tone output
indicator 103, e.g., a light or buzzer, coupled to the
DTMF encoder output, to indicate to a user when the auto-
dialer 100 is pulsing out tones. In this manner, the
auto-dialer 100 provides a signal to the user that the
user should keep the auto-dialer 100 in close proximity
to the receiver's microphone to avoid errors.
In addition to the use of a proximity sensor
228, the housing of the auto-dialer 100 of the present
invention (see, Figs. l0A-lOD) is designed to be
relatively small making it easy to visually or manually
center the speaker 114 of the auto-dialer 100 over a
telephone handset's microphone 116. Tests have shown
that failing to properly align the speaker 114 with the
center of the microphone 116 can result in a wide range
in terms of signal intensity as detected by the
microphone 116. In addition to being small in size, the
housing includes a circular area designed to easily mate
with the speaker end of a standard handset. Thus, by the
design of autodialer's housing, a user can easily align
the center of the transducer with the center of an
interfacing microphone or speaker so as to provide for
the uniform transmission/reception of tones.
Referring briefly to Fig. 10A, a bottom view o~
the auto-dialer housing 101 is illustrated. As
illustrated, the auto-dialer 100 has a housing 101 which
should be placed closer to the
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has a head 103 with openings 105 to allow sound out.
From the bottom planar view of Fig. 10A, the head has a
generally circular appearance. The head 103 is designed
to be smaller in diameter than most telephone
mouthpieces, e.g., less than 6 cm in diameter. In one
embodiment, the circular head 103 is designed to be
approximately 34 millimeters (mm) in diameter. This is
sufficiently small to permit the auto-dialer 100 to be
easily centered, by visual inspection, with the
microphone of a wide variety of telephone handsets
including the handset of a NYNEX public telephone which,
in one field test, was found to contain a microphone
having a diameter of approximately 6 cm. While other
microphones used in mouthpieces will vary in size, the
relatively small size of the head 103 should permit easy,
yet relatively precise, visual and manual alignment,
e.g., centering with most telephone handset based
microphones in use today.
The ability to visually center the auto-dialer
100 of the present invention with the microphone of a
handset is important because mouthpieces on handsets
frequently vary in size and shape making it difficult to
use a circular gasket or other device to aid in the
centering of auto-dialer speakers with the microphone
contained in a mouthpiece of an increasing number of
telephones, which do not have a locating ring as was the
custom with telephones built many years ago.
Thus, because of the shape, e.g., generally
circular appearance when viewed from above or below, and
small size of the head 103 of the auto-dialer 100 tt is
possible to easily center it using visual techniques
which may not be possible using a rectangular shaped
housing or other type of housing which makes it difficult
to see the microphone 118, and thus its center, when the
auto-dialer 100 is placed in close proximity thereto.
Other features of the present invention are
also designed to enhance the efficiency of the transfer
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of and acoustic DTMF signal to the microphone 116 of a
telephone handset 121. For example, in one embodiment of
the present invention a relatively sound transparent
barrier, as opposed to a sound baffling barrier, is used
to encircle the area of the autodialer's case near audio
outputs 105. The barriex is used to reduce the resulting
harmonics when the case of the auto-dialer 100 makes
contact with an interfacing, e.g., telephone. However,
the barrier is not designed to occlude ambient sound from
entering the column between the device and microphone.
Testing has shown that when using a baffle in
conjunction with an electret microphone it is important
to maintain at least a 25% open air flow between the
autodialer's speaker and the microphone.
Accordingly, while an isolating barrier, such
as a gasket, may be used between the autodialer's speaker
114 and the microphone 116 to reduce the level of ambient
noise transmitted to the microphone 116, in general,
higher device output should be provided in lieu of such
an isolating barrier. The use of higher signal output
levels is generally more effective than the use of such
isolating barriers because there will normally be some
ambient noise present during the use of an auto-dialer
100 regardless of the presence of a gasket since, e.g.,
most handset housings are reasonably good conduits for
ambient sound to the microphone 116.
Therefore, while a gasket interface between the
auto-dialer 100 and the interfacing microphone may be
appropriate to reduce the possibility of harmonics
arising from the movement of the auto-dialer 100 on the
surface of the microphone, the gasket should not be
intended to provide isolation of the generated tones from
the ambient noise environment.
The use of high audio output signal levels,
e.g., 95 to 114 dB(spl), has proved to present advantages
with regard to transmitting a DTMF signal to carbon
microphones found in handsets 121. Significantly,
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testing has shown that such relatively high power levels
do not present problems when the auto-dialer 100 is used
with electret microphones, which are generally more
efficient than carbon microphones at transferring
5 acoustic signal into electrical signals, as long as there
exists an air escape route in any baffle positioned
between the interface of the auto-dialer 100 and the
housing of the electret microphone. In particular, tests
were performed using a 115 d B (spl) output level with a
10 electret microphone and no significant deterioration in
the signal to noise ration (S/N) or increase in the
relative power level of the third tore signal were
detected.
While a transmitted tone of 115 dHm will most
15 likely be received having an instantaneous power level in
excess of the average power level permitted by the Bell
System Spec 103 hereby expressly incorporated by
reference, for a signal used for standard call
processing, the average power level as defined in the
20 specification is the average power level of a signal
received over a three second period. Since DTMF tones
must be followed by an inter-digit period of at least 35-
40 milliseconds, as long as the tone, even at the 115 dBm
level, is generated for less than one second, the
25 resulting average power level received at the receiving
call processing switch will fall within the maximum
permitted power level limits.
D. Manufacturing Tolerances And Their Effects On
30 The Production Of Recognizable Tones
The various methods of avoiding some of the
normal errors associated with the acoustic transmission
and reception of DTMF signals discussed above rely on the
35 ability to accurately generate DTMF tones of a desired or
nominal frequency, intensity and duration.
The ability to generate an audio tone at a
designated frequency is a function of the hardware being
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used to produce the tone. Despite manufacturer's claims
of close tolerances among similarly manufactured devices
used in auto-dialers, it has been found that auto-dialer
components and output devices in particular, vary in a
significant manner with regard to the frequencies and
power levels needed for accurate operation of an auto-
dialer. For example, a variety of speakers from several
manufacturers while being presented by the manufactures
as being "identical" produced a wide range of variations
with regard to their efficiency and ability to accurately
generate particular tones.
Since the degree of variations between
components is largely a function of the cost of the
components, as one attempts to manufacture an auto-dialer
at a commercially acceptable cost, the variation in the
outputs of the auto-dialers produced can be significant.
In one test, otherwise identical auto-dialers
manufactured by the same manufacturer to commercial
tolerances exhibited output variations of as much as 15%
in signal acoustic intensity levels. In addition, they
exhibited variations in twist for the same tone-pair of
between +3 dBm and -3 dBm.
While digital signal processing employed by
some telephone switching systems may be capable of
tolerating some of the variations that exist between
known auto dialers outputs, to insure acceptable error
rates and compatibility with the vast majority of
telephone systems, a method of generating precisely
defined, stable tones is required.
In accordance with one embodiment of the
present invention, variations in signal output that exist
between auto-dialers are minimized by the individual
calibration of each auto-dialer 100.
In particular, in accordance with the present
invention, the auto-dialer 100 is designed to be
programmable and to support both factory and auto
calibration features which permit the auto-dialer 100 to
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be calibrated and adjusted by varying various calibration
parameters stored in the RAM 108 and/or ROM 106. These
calibration parameters control, e.g., the acoustic sound
pressure level of each tone in a tone pair that may be
generated as well as the frequency of the individual Lo-
band and Hi-band tones that are generated. In the event
of remote re calibration, pre-established bench marking
tone levels are generated so as to compensate for
microphone related transmission system line losses and
distortions thus permitting accurate recalibration of
tone characteristics.
In addition, calibration of the system clock
may also be performed either at the factory or from a
remote location, e.g., via communication of clock
calibration information over a telephone system. For
example, in one embodiment, the auto-dialer 100 is
responsive to a calibration signal to permit the setting
of the auto-dialer's system clock and, upon the
subsequent receipt of another pre-determined signal,
e.g., a sequence of tones stored in memory permits the
calibration of the clock based on the internal clock's
deviation; from the standard time since the clock's
previous setting, as measured by a calibration device.
Thus, in accordance with this embodiment, the auto-dialer
100, upon the receipt of a pre-selected and/or remotely
generated signal, permits the establishment of a system
time by setting the auto-dialer's clock, and, upon
subsequent receipt of another pre-defined signal, permits
the calibration of such system-time based on the
deviation in time which occurred from the time the-auto-
dialer's clock was last set. Calibration of a clock in
this fashion, i.e., establishing the number of counts
that the clock being calibrated is divergent from a
standard based not only on the actual current difference,
but also the time interval since it was last calibrated,
permits a much higher degree of future accuracy than can
be achieved by simply setting and resetting the actual
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time.
As will be discussed further below, the auto-
calibration and other programming features of the auto
dialer 100 of the present invention give it the ability
to monitor, process, and store, the transmission-related
characteristics of output tones, and to cause the device
and its components to alter its output in accordance with
pre-established characteristics or output parameters
stored in the RAM 108 or ROM 106. Furthermore such auto-
calibration procedures/features may be triggered by
either the auto-dialer 100 receiving a pre-selected group
of tones, or upon other pre-determined conditions , e.g.,
first use of the auto-dialer 100 after a 24 hour period
of inactivity, when a thermistor indicates a change in
temperature, when the battery voltage is at pre-
determined levels, etc.
Thus, in accordance with the present invention,
the microprocessor 104 can receive calibration commands
instructing it to initiate a calibration routine via,
e.g., the DTMF decoder circuit 112.
These commands may be received acoustically,
e.g., from a speaker in a telephone handset or from
alternative command generator devices (e. g. manufacturing
test equipment, automated teller machines, etc.) via
either electrical or acoustical connections to the auto-
dialer 100, e.g., a secondary input/output device 109
coupled to the microprocessor 104. Accordingly,
calibration may be done either remotely, e.g., by
connecting the auto-dialer 100 acoustically to
calibration equipment using a standard telephone or
directly by placing the auto-dialer 100 in actual wired
connection to calibration equipment.
As part of the calibration routine, the auto-
dialer 100 generates one or more of the Lo-band tones and
Hi-band tones in a predetermined sequence. These tones
are received by ca'_~.~ration equipment acoustically
coupled to the auto-dialer 100 and checked to determine
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how much the received tone output varies from the desired
tone output in terms of such characteristics as
frequency, output level and duration. Using the
information gained in this manner, the calibration
equipment determines the adjustments required in the
parameters used to control the generation of each tone
signal to correct for the detected deviations from the
desired tone characteristics. The adjustments are then
supplied to the auto-dialer 100 through, e.g., a series
of acoustic signals, representing, e.g., programming
commands and control data, which cause the auto-dialer
100 to store adjustment parameters in the RAM 108. In
this manner, each auto-dialer 100 of the present
invention can receive commands causing it to adjust the
level and fundamental frequency of each tone pair and the
overall twist of the tone pair. Accordingly each
manufactured auto-dialer 100 can be easily calibrated on
an individual basis to maximize auto-dialer performance.
Furthermore, because such calibration can be done over a
standard telephone line, individual auto-dialers 100 can
be calibrated periodically, if necessary, by calling a
central office or as part of a routine auto-dialer
program update procedure conducted via a routine
telephone call to an update service.
The adjustment parameters stored in the auto-
dialer 100 in response to acoustic programming commands
are used by the processor 104 when generating DTMF tones
in the future. Thus, the auto-dialer 100 can be easily
calibrated and programmed to compensate for manufacturing
variations. In the described embodiment, the auto-dialer
100 contains software enabling the auto-dialer s output
to be adjusted to conform to pre-determined standards,
e.g., the standards set for telephone dialing and touch
tone recognition, in response to a series of signals,
such as a series of DTMF tones, received from calibration
equipment.
Generally, the auto-dialer 100, under the
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control of the processor 104, can, upon receiving a pre-
determined string of tones, respond with either a pre-
established selection of data as indicated by the
received string, or, if such selection is not available,
5 respond with other data. Thus, the auto-dialer 100 will
transmit pre-defined diagnostic and other condition
indicative information upon the receipt of pre-defined
tones.
In one embodiment, the auto-dialer 100,
10 contains software enabling the calibration of the auto-
dialer's audio output to conform to pre-determined
standards whereby calibration equipment provides a pre-
established set of tones which causes the auto-dialer 100
to send a string of tones which represent the spectrum of
15 tones which the auto-dialer 100 will, in normal
operation, be called upon to create, and the provision by
the calibration setup equipment to provide instructions
to the device to alter characteristics of any tone (or
aspect there of) which fails to conform to the pre-
20 established standard.
Because the auto-dialer 100 of the present
invention provides for the storage of calibration
information such as the adjustment parameters in its RAM
108 and the use of such parameters when generating DTMF
25 tones, the need to use high tolerance components in the
auto-dialer 100, and its audio section in particular, is
greatly reduced. This permits the use of significantly
lower tolerance components than would be possible if such
calibration was not supported.
30 This decrease in component costs helps to
offset the incremental cost of incorporating the
calibration features described above into the auto-dialer
100 of the present invention.
The auto-calibration feature of the present
35 invention also helps to offset the impact temperature
changes will have on the output of the auto-dialer 100.
As the temperature changes, the mechanical
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51
characteristics, e.g., shape of the auto-dialer housing
101, may change slightly. In addition, battery voltage
and other electrical aspects may also change. These
variations may have an effect on the output of the auto-
s dialer 100, both in terms of actual tone outputs
(frequencies and their levels) as the housing serves as a
resonating chamber of the auto-dialer's audio system.
However, as a result of the auto-calibration
process, instructions can be provided to the auto-dialer
100 to compensate and correct its signal output for such
changes in temperature thereby providing a degree of
output accuracy that might not be possible absent such an
auto-calibration feature.
Due to the inherent, unique harmonics that are
associated with each individual auto-dialer 100 because
of manufacturing variations in both housings and
components, as discussed above, calibration of auto-
dialers 100 should be performed on an individual basis.
One method that has been found to provide
satisfactory results is to monitor the signal generated,
in response to the auto-dialer's output through a
telephone system 122, in conjunction with other
calibration equipment In such a case, the signal that is
monitored is the signal output by the telephone system
122 to a telephone line connecting the telephone system
122 to, e.g., centrally located calibration equipment.
To insure that the auto-dialer 100- will work
properly with a wide range of telephone systems,
calibration may be performed using data that is obtained
from studying an assortment of different microphones and
anticipated line-losses. During calibration, equipment
that is programmed to analyze the received signal
generated from the output of the auto-dialer 100 may be
used to perform the required calibration analysis and
calculate the required adjustment that may have to be
made to the auto-dialer's control parameters to insure
the generation of output signals, e.g., tones that will
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be recognizable to standard telephone switching devices.
In one embodiment, when determining the levels
which each auto-dialer 100 should be calibrated to,
carbon microphones are used as part of the calibration
process. Carbon microphones that have been used for at
least 30 days should be used to insure that the packing
effects of the carbon granules contained in the
microphone will represent those which can be expected
during normal use. Furthermore, when using handsets 121
with carbon microphones for establishing calibration
levels " the handset 121 should be, for best calibration
results, those handsets which were stored vertically.
In addition, calibration levels should be performed with
the handsets located at a 30 degree angle relative to the
horizontal and with the auto-dialer's speaker 114 placed
in close proximity to the handsets microphone 118.
A plurality of handsets should be used for
determining calibration levels. As auto-dialer
components and housings will not be identical it is
important that the calibration process be performed in
such a manner as to test, modify, and re-test each auto-
dialer 100 until the desired output levels and signal
characteristics are achieved.
In addition to calibration features that are
designed to support the calibration of the auto-dialer
100 in response to external commands or signals, e.g. a
series of encoded DTMF tones, the auto-dialer 100 of the
present invention incorporates several automatic
calibration features that are designed to increase
reliability. For example, as will be discussed further
below, the auto-dialer 100 may include a temperature
sensor 105 as illustrated in Fig. 3. In response to the
output of the temperature sensor 105, the microprocessor
104 adjusts the output signal levels and or frequency, to
compensate for, e.g., temperature related changes to the
auto-dialer housing or audio output components 110, 114
that may effect the precision of the DTMF signals being
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generated by the auto-dialer 100.
In addition, sensors, such as the voltage
comparator 210, may be used to check that their is
._ sufficient battery power to accurately generate the
desired tones and to signal a user when battery power is
-- low, e.g., via the display 202.
While the ability of the auto-dialer 100 to be
programmed to adjust the output frequency of generated
tones has been described with regard to calibration
features, it is also worthwhile to note that the auto-
dialer 100 can, upon receiving a predetermined set of
tones, accept and add/replace to the existing listing of
acceptable tones to be generated or received, and that
those tone pairs may or may not be among those commonly
used for the transmission of telephonic communications.
II. Security Features
In addition to the above described error
avoidance features, the auto-dialer 100 of the present
invention incorporates numerous security features which
are intended to enhance the security of both the data
contained in the memory of the auto-dialer 100 and other
important data which is transmitted by the auto-dialer
100 over a telephone line. The security features
discussed below along with the auto-dialer's
programmability, make the auto-dialer 100 of the present
invention particularly well suited for use as a
transaction card device wherein the auto-dialer 100 is
programmed with billing and other credit information
which can be used in accordance with conventional credit,
debit and other protocols and transactions.
In order to minimize the risk of fraud, the
,_
auto-dialer 100 can be programmed to transmit only data
which will enable an authorized and enabled service
provider to decode r_'~? system-clock based encryption of
the device number, with only an account routing prefix.
Specifically, the device would not store an actual
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account number. Instead, it would only store that data
which numerically describes the service provider.
In this scenario, the service provider would
use the decrypted body number as the key to the
corresponding account in the database. The routing
prefix would be the standard routing numeric to direct
the data to the appropriate service (credit/debit)
provider using the traditional closed (non-publicly
accessible) private network which exists for credit/debit
authorizations.
By using this method of account information
transfer and look-up, the data which is generated by the
device is of no value as the device does not contain an
account number which is, by itself, capable of being used
as a credit/debit transaction.
Significantly, the acoustic coupling and
programming features of the auto -dialer 100 permit the
auto-dialer 100 to be used with standard telephone
devices without the need for a direct electrical coupling
to a receiving device generally required by other smart
card type devices.
In the event of a security breach with respect
to any aspect of the system-time or encryption techniques
used in the auto-dialer 100, over-the-phone updates can
be provided to each auto-dialer 100 to modify the key or
keys programmed into the auto-dialer 100, the system-
clock, or any other parameter which affects the security
of the auto-dialer 100.
A. Encryption of Data Into DTMF Tones
A data encryption feature, which may also be
described as a data encoding feature, of the present
invention provides security for data transmitted by the
auto-dialer 100. This feature will now be described.
Many characteristics of DTMF tones may be varied without
making a DTMF tone signal unrecognizable to standard DTMF
tone detection circuitry. For example, the duration of
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individual tone signals, the twist associated with a DTMF
tone pair, and the period of silence between DTMF tone
signals being transmitted in a sequence, referred to as
__ the interdigit period, may be varied over a wide range
5 without affecting the ability of standard DTMF detectors
.'- to recognize the tone pairs being transmitted. In
addition, it may also be possible to vary the transmitted
frequency of the Lo-band and/or Hi-band tones slightly
without substantially effecting the ability of a
10 receiving device to detect and decode each DTMF tone pair
based on the standard fundamental frequencies of the
tones in the tone pair.
Such variations in a DTMF signal are possible
because standard DTMF detectors are designed to allow for
15 the wide variations in the time it takes different people
to enter telephone numbers, e.g., in teens of how long
some people hold keys or wait before pressing a next key
representing the next digit of a telephone number, DTMF
detectors accept a wide range of durations and silence
20 periods between DTMF signals before they will disconnect
because of the continued receipt of a DTMF tone or an
extended period of silence.
As discussed briefly above, the existing
standard for DTMF signals specifies a minimum signal
25 duration, minimum period of silence between signals and a
range of twist levels which are required for a DTMF
signal to be considered valid. For example, standard
telephone DTMF signal detectors which are used to detect
the tone pairs that make up a DTMF signal require the
30 following for a tone pair to be properly detected:
. 1. The tone-pair must be present for at
- least 35-40 milliseconds.
35 2. The tone-pair must include one tone,
and only one tone, from the pre-
selected Hi frequency band group
of 4 possible Hi frequency tones
and one tone, and only one tone,
40 from the pre-selected Lo
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frequency band group of four Lo
frequency tones.
3. The level of the Hi frequency tone
can not be greater than 4 dBm more or
8 dBm less than the Lo frequency
tone.
4. The level of both the Hi and Lo
frequency tones of each tone
pair must be in the range of 0
to -25 dBm.
5. Consecutive tone-pairs must be
separated by at least 35-40
milliseconds of silence.
With modern digital signal processing equipment
it is possible to accurately measure the characteristics
of a DTMF signal that can be varied without affecting the
validity of the DTMF signal. Furthermore, it is possible
to use the auto-dialer 100 of the present invention, to
generate DTMF and non-DTMF signals having specific
characteristics, e.g. tone and inter-digit durations,
amplitudes, and twist levels.
By assigning selected values to the different
alterable characteristics of a DTMF signal that can be
changed without affecting the signal s ability to meet
the above described requirements for a valid DTMF signal,
it becomes possible to encode or encrypt information into
a DTMF signal without affecting the validity of the DTMF
signal for use and detection with conventional call
processing equipment. For example, it is possible to
define that, e.g., a particular period of silence between
tone pairs of a DTMF signal will represent one character
while another period of silence will represent a second
character. Similarly a particular level of twist may be
use to represent one value or character while another
level of twist may be used to represent a different value
of character. DTMF tone duration may be used in the same
manner to represent yet other informa'ion. The overall
aggregate power level of a tone pair may also be used to
represent data. In addition, frequency variations or the
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deviation of the high and low tones from pre-selected
frequencies within the range of recognizable DTMF tone
frequencies may also be used to represent data. These
__ alterable characteristics can be used individually to
represent information or can be used in combination.
.'. It has been found that when using the
individual signal level of the Hi-band and Lo-band tones
of a tone pair, or the overall signal level of the
combined tone-pair to represent information, it is
desirable to send a reference level to the receiver to
serve as a measure against which to compare the level of
other tones. This reference level may be determined from
the level of a tone pair located in a pre-determined,
e.g., fixed place in the series of tone pairs being
transmitted, e.g., at every fourth tone pair, or it may
be transmitted with a tone pair having a predetermined
duration or other characteristic, e.g., the first tone
pair having a tone duration of 60 ms. By sending
reference levels to the receiving device in this manner,
it is possible to compensate for varying conditions,
e.g., microphones, line losses, etc., which effect tones
transmitted from the auto-dialer 100.
An example of the encoding scheme of the
present invention will now be described below with
reference to Figs. 11 through 13.
Referring now to Fig. 11, possible values for
various characteristics of a tone pair of a DTMF signal
representing the digit three are illustrated. As
discussed above, it is possible to control these
characteristics to represent data in accordance with the
present invention.
Referring now to Fig. 12A there is illustrated
a Lo-tone level to data conversion table that can be used
in accordance with the present invention to convert the
Lo-tone level of an encoded tone pair into data. By
monitoring the received signal and detecting the level of
the Lo-band tone, e.g., the value -6 dBm (as measured at
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5a
the DTMF decoder circuit 112) in the example of Fig. 11,
it is possible to use the conversion table to convert
this value into a data value by a simple look-up
operation. Thus, by looking up the value -6 dBm in the
table of Fig. 12A it can be determined that the number 7
was being transmitted.
Fig. 12B which illustrates a Hi-band tone level
to data conversion table, can be used to convert the Hi-
band tone level into data in a similar manner, e.g., by
monitoring the received signal and detecting or measuring
the level of the Hi-band tone signal. Performing a look-
up operation using the exemplary data of Fig. 11
indicates that the -6 dBm signal level of the Hi-band
tone signal represent the number 7.
Similar look-up operations may be used to
convert other detected tone pair signal values into data.
For example, the table of 12C can be used to convert tone
pair duration values into data while the table
illustrated in Fig. 12D can be used to convert tone pair
interdigit period values into data. Similarly the tables
of Fig. 12E and 12F can be used to convert measured
frequency deviation values into data while the table of
Fig. 12G can be used to convert twist values into data.
Referring now to Fig. 13 the results of using
the tables of Figs. 12A-12G to convert, i.e., decode, the
measured signal values of Fig. 11 into data are
illustrated.
Thus, as illustrated in the example set forth
in Figs. 11-13, it is possible to encode a seven digit
number (7718832), e.g., a calling card number, into the
DTMF tone pair representing the digit three without
affecting the ability of a standard DTMF detector to
decode the tone pair. Furthermore, in the described
example the additional calling card number was conveyed
in approximately 75% less time than that which is
normally required ~v~r manual input.
Thus, as illustrated by this example, it is
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possible to transmit encoded DTMF signals which satisfy
the minimum DTMF call processing standards while
conveying both the conventional dialed digit, e.g., the
__ digit three, as well as a substantial amount of
additional information.
While the above described example illustrates
the decoding of encoded DTMF signals it is possible to
encode data using the same data tables that are used for
decoding purposes as described above.
To add even a greater number of possibilities,
the various alterable characteristics of a DTMF signal
may be used in combination to represent values or
characters. For example, a particular period of tone
duration combined with a particular degree of twist may
be used to represent one value while a second period of
tone duration and a second level of twist may represent a
second value.
Furthermore, to provide added security the
encryption mechanism may assign different values to the
same alterable characteristics of a DTMF tone pair as a
function of the standard symbol/digit the DTMF tone pair
represents. For example, a-particular period of silence
following the DTMF tone pair representing the digit one
may be assigned a different value than the same period of
silence following the DTMF tone pair representing the
digit two.
It is readily apparent that a very large number
of encoding combinations based on the numerous possible
alterations that can be made to a DTMF signal without
affecting the ability of standard telephone switching
circuitry to detect and decode the underlying DTMF signal
are possible. Thus, the above method of encoding data
into a series of DTMF signals, makes it possible to
transparently encode data such as calling card number or
billing information into a telephone number represented
as a series of DTMF signals.
In accordance with one embodiment of the
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present invention, the auto-dialer 100 encrypts sensitive
information, such as the user's calling card number,
directly into the telephone number being called, using
the above encoding technique. In accordance with such an
5 embodiment, the receiving system that detects the DTMF
tones monitors the alterable characteristics of the DTMF
signal that are being used for encoding purposes and then
decodes the calling card information based on encoding
information stored in a data base. In this manner, only
10 the telephone number need be transmitted as a DTMF signal
with the normal need to transmit a separate DTMF signal
representing the calling card number, billing, calling
party, or other identification information or data being
avoided by encoding such information directly into the
15 telephone number.
In a sense, the encoding method of the present
invention may be described as the indexing of the
alterable characteristics of a DTMF tone. In the case of
a device seeking to transfer information using encoded
20 DTMF tones, the device may use a lookup table containing
a list of the characteristic that should be altered and
how the characteristic should be altered to represent a
particular symbol or number. In this manner, the value
to be encoded is used as an index into the lookup table
25 such as the exemplary tables illustrated in Figs. 12A -
12G, of a transmitting device such as the auto-dialer
100.
For a receiving device, the measured value of a
particular alterable characteristic of.a DTMF signal
30 being monitored serves as an index into a lookup database
or table such as the ones illustrated in Figs. 12A -12G,
containing information on the symbol or number
represented by the particular characteristic or
characteristics of the DTMF signal being monitored. By
35 monitoring a particular alterable characteristic of a
DTMF signal and comparing measured signal values to the
values stored in the lookup table, a device is thus able
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to easily decode encoded DTMF signals.
In the above described manner encoded DTMF
signals can be readily encoded and decoded using a lookup
_, table or database and a device for controlling or
monitoring the alterable characteristics of the DTMF
;_ signal being generated/received. Thus, the encoding
technique can be implemented using relatively simple
circuitry. Furthermore, the encoding and decoding of
encoded DTMF signals can be performed without affecting
the ability of a standard DTMF decoding circuit to decode
the DTMF signal to determine the symbols/numbers
represented by the standard tone pairs that comprise the
encoded DTMF signal.
In accordance with the present invention, the
relevant database needed for encoding/decoding encoded
DTMF signals is stored in both the auto-dialer 100 being
used to encode the information and the database being
used to decode the information encoded into the DTMF
signal. The ROM 106 of the auto-dialer 106 may be used
to store such a database. However, for added security,
the database may be stored in RAM 108 and periodically
revised, e.g., in response to acoustic reprogramming
commands received via a telephone.
As discussed above, in one embodiment of the
present invention, the auto-dialer 100, uses the above
described encoding method to encode calling card, long
distance carrier information and other identification
information, such as device body or identification number
information, directly into the destination telephone
number. This information is then decoded by the DTMF
decoding system which receives the series of encoded DTMF
signals, representing the telephone number, and processes
accordingly. In this manner, a user is able to place a
call and charge the call to a calling card or credit card
without having to manually input the credit information
thereby reducing the possibility of human errors.
Furthermore, the device, using this indexed approach,
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can transmit data much faster than would otherwise be
possible using conventional DTMF tones.
As discussed briefly above, a data string using
indexed tone characteristics in the above-described
manner can be processed much faster than a data string
using only conventional DTMF signals to represent the
same amount of data. A reduction in the time needed to
receive and decode the data necessary to complete a
transaction, e.g., determine a destination number,
account number, etc., will reduce the requirement for
additional tone detection equipment, i.e., switching
equipment, as well as reduce the un-billable time that a
long-distance carrier must absorb before it is able to
connect the call and initiate billing. Accordingly, the
encoding technique of the present offers important
advantages over know systems.
These advantages are due in part to the
inherent "data compression" feature of the encoding
method of the present invention which permits information
to be encoded into a DTMF signal without causing a
significant increase, in the time required to send the
DTMF signal with its underlying information, e.g.,
telephone number information.
As discussed above, standard DTMF tones were
designed for the transmission and detection of only a
single number or character of DTMF alphabet (1-9, 0, a,
b, c, d, *, #)) for each DTMF tone pair transmitted. As
standard DTMF detection equipment requires a minimum
tone-length of 40 milliseconds and a minimum inter-digit
period of 35 milliseconds, the effective throughput of
DTMF data can be no greater than 13 characters per
second, with an alphabet limitation of only those
contained in the DTMF alphabet.
As a an example, consider how long it would
take to transmit Account # 123-45-6789. Using
conventional DTMF, each numeric would be transmitted at
the minimum full-cycle time period of 75 milliseconds.
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At 13 characters per second, the minimum time required to
transmit the account number would be 675 milliseconds.
Using the encoding method of the present
_. invention, it is possible to substantially increase this
data transfer rate. The increase in the effective
-- transmission rate of data, e.g., the data compression
feature referred to above, is achieved by the encoding of
a standard DTMF signal such that alterable
characteristics of the signal are controlled to represent
data being transmitted. Thus, it is possible to "piggy-
back" additional information on a standard DTMF signal
additional information which can relate to, e.g., the
destination phone number or billing information.
Tests have indicated that the encoding
technique of the present invention can increase the
actual data throughput of information using DTMF signals
from the current maximum through-put of about 13
characters per second to around 500 characters per
second.
This level of increased transmission rates can
be achieved through the indexing of the DTMF tones using
various measurable characteristics. For example, if the
indexing scheme ascribes 15 values to both the tone
length and inter-digit length, 3 values to the level of
each fundamental frequency of each tone-pair, 2 levels of
aggregate tone power levels, as well as the 16 actual
frequencies, the indexed alphabet for each tone-pair is
64,800 possible variations. A modified alphabet to take
advantage of this expanded set can easily include groups
of the numeric characters, including all combinations of
the 0-9 set.
. If one further assumes that the range of tone-
lengths to be 40 to 110 milliseconds, with 5 milliseconds
between each period, and 20 to 48 milliseconds for inter-
digit silence periods, with 2 millisecond increments, the
average indexed-signal period is 109 milliseconds, or 8
tone-sets per second.
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Therefore, the indexed method can yield 56
digits per second. At this rate of transmission, the
time required to transmit 123-45-7890 would be .18
seconds.
Further efficiencies can be achieved through
the use of other compression techniques well-known in the
art. Additionally, as the time needed for standard
digital signal processing equipment to resolve an
incoming signal is generally the inverse of the signal,
the minimum signal length, as well as the increments of
varying signal lengths, when using DTMF signals, can be
reduced to a minimum tone signal period of the lowest
frequency in its domain, e.g., 597 Hz, or 1.675
milliseconds. At this rate, allowing a similar increment
for each one increment and an increment of 1 millisecond
for the inter-digit period, the effective throughput
increases to over 174 characters per second.
The speed of data transmission using this
technique can be increased by orders of magnitude by
increasing the number of frequencies simultaneously
transmitted, the number of frequencies to chose from, by
using higher frequencies than those used in the DTMF
spectrum, as well as the transmission of out-of-band
tones during otherwise quiescent periods.
Thus, as described above, the auto-dialer 100
has the ability to use various tone characteristics,
e.g., the duration of one or more tone pairs or the
fundamental frequencies thereof, the aggregate power
level of a tone-pair or either of its fundamental
frequencies, etc. for the transmission of strings of
data. In one embodiment, the particular characteristics
used to encode data when transmitting data to a first
device, e.g., a local switching office, are different
than those used to transmit to a second different device,
e.g., an enhanced switching office. Accordingly, in such
an embodiment, the particular encrypting or encoding
performed is a function of the device to which the auto-
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dialer 100 is transmitting the data. To support this
feature, the auto -dialer 100 is programmed to encrypt
data strings when it can be reasonably assumed that
__ decoding equipment capable of decoding encoded DTMF
5 signals will be available on the receiving end. In other
:- cases, in such an embodiment, when there is no assurance
that the switching center which will receive the
generated tones will be able to decode an encoded DTMF
signal, the auto-dialer 100 is programmed to use
10 conventional DTMF exclusively in its transmissions.
While the data encoding technique of the
present invention is described in terms of DTMF tones,
the encoding technique is generally applicable to any
signaling system which uses one or more frequency-based
15 signals to communicate data. For example, it is possible
to encode data into a signal which comprises a series of
tones using, e.g., tone length, frequency , amplitude and
interdigit duration. One should note that in most
publicly accessible switching systems certain frequencies
20 are restricted from use for switching or data
transmission purposes.
Referring now to Fig. 6, there is illustrated a
flow chart representing the steps involved with placing a
call using the auto-dialer 100 of the present invention
25 which encodes calling card and/or calling service
information directly into the series of DTMF tones which
represent the destination telephone number.
The flow chart of Fig. 6 assumes that an auto-
dialer 100 is preprogrammed with one or more carrier
30 access numbers and phone numbers as well as the encoding
information, e.g., data characteristic/information
tables, such as those illustrated in Figs. 12A-12G,
needed to generate encoded DTMF tones. As will be
discussed below, the programming of user-accessible
35 aspects of the auto-dialer 100 may be done, e.g., at the
factory , from a remote location via use of the acoustic
interface of the auto -dialer 100, by manipulation of
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device keys, or in conjunction with another coupling
device which can either generate acoustic signals or is
electrically connected to the device.
As illustrated in Fig. 6, the calling
transaction of the present invention starts with a
decision to make a credit card call as indicated in step
1100. The user of the auto-dialer 100 accepts the
default credit card number from the numbers stored in the
auto -dialer or, if desired, selects a credit card number
or 100 as indicated in step 1102. Next, the user selects
one of the destination phone numbers stored in the auto-
dialer 100 or inputs into the auto-dialer 100, using the
input device 105, the telephone number to be called as
indicated in step 1104.
In the next step 1106, the user places the
speaker 114 of the auto-dialer 100 in close proximity to
the mouthpiece of a telephone and enables, e.g., by
pressing a key, the auto -dialer 100 to output the
access number, i.e., telephone number of the selected
carrier, e.g., the carrier which has been pre-programmed
to handle the particular call. The local office, which
monitors this output, connects the line to the indicated
carrier. When it is believed that the local office is
not capable of decoding indexed tones, only traditional
DTMF tones are generated by the auto-dialer 100 for this
part of the call transaction.
Upon connection with the carrier, the carrier
switch provides an audible signal to the user to depress
a button to send the next string of data which includes
the selected destination phone number as a series of
acoustic encoded DTMF signals with the calling card
number information and/or other information being encoded
by the auto-dialer 100 into the DTMF signals that
represent the destination telephone number. Device
identification information, e.g., a unique device body
number, may also be encoded into the telephone number as
well. The sequence described above can be altered, on a
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carrier by carrier basis, such that the sequence matches
the data processing protocol of the carrier or its
ability to decode embedded data. Further, the
__ requirement of a second button-push to initiate the
transmission of the second string of data can be
-- eliminated if the time requirement for the call to be
connected with the second switch (e. g. the long distance
carrier) can be reasonably predicted.
Upon receiving the encoded DTMF signals, in
accordance with the present invention, the circuitry
which receives the encoded DTMF signals decodes the
received DTMF signals to determine, e.g., the desired
destination phone number, the calling card number
information and/or the device identification information
which is encoded into the DTMF signals representing the
received telephone number.
At this point, as illustrated by step 1108, the
switching circuit, e.g., system, e.g., the long distance
carrier checks a database, e.g., a central data base
containing information about each auto-dialer 100 to
determine if the device is an authorized or unauthorized,
e.g., stolen, device. In addition, the provided accounr_
billing information, e.g., credit card number, is checked
to determine if it is a valid number.
If the auto-dialer 100, used to place the call,
is an authorized device and if the calling card number is
valid, the call is placed as indicated in step 1110.
However, if the calling card number is invalid, the call
is rejected and not placed. In the event that device
identification information encoded into the destination
telephone number is determined to be invalid, the auto-
- dialer 100, is disabled, by, e.g., being sent a series of
acoustic tones to which the auto-dialer 100 is programmed
to respond by deactivating itself.
In one embodiment, those tones which cause the
device to become deactivated are preceded by a voice
prompt by the switching system to the caller indicating
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that updated information is available and prompts the
caller to hold the device to the earpiece and press a
key, which signals the switch system that the device is
ready to receive the instruction, e.g., in this case, the
deactivation signal.
The above described calling procedure offers
many security and convenience advantages over the
standard calling procedure previously described with
regard to Fig. 1.
First, by outputting the account billing
information using the auto-dialer 100's indexing system,
a user need not input the sensitive billing information
using a viewable keypad, e.g., the telephone keypad.
Accordingly, a person visually observing a call
transaction cannot obtain the billing data from what he
observes and, therefore thus, use the data for
unauthorized purposes.
Second, because the calling card number is
encoded into the telephone number, it may not be apparent
to an observer that a calling card number is being
transmitted. Furthermore, when the auto-dialer's system
clock is used to encrypt the calling card number
information, the recorded dialing sequence will only
remain valid for a short period of time determined by the
time period the specific particular encryption seed
number is used.
Furthermore, even if the dialing sequence with
the encoded calling card number is recorded, the
recording can not be used directly to gain access to a
long distance carrier to call numbers other than the
number that was being dialed. As a result, the value of
the recorded and subsequently decoded data is of little
value due to its relatively short useful life and its
restricted use during the validity period.
Thus, the croblems relating to an unauthorized
user recording a calling card number, which, in the known
systems, is transmitted as a separate signal from the
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telephone number, and then playing it back to place calls
to other telephone numbers are avoided.
Referring now to Fig. 7, the signaling
., relationship between the various devices involved with
completing a call transaction using encoded DTMF signals,
:_ in accordance with the steps illustrated in Fig. 6, is
illustrated.
As illustrated, acoustic signals 116 from the
auto-dialer 100, including, e.g., encoded DTMF signals,
if the receiving circuit is known to be capable of
decoding encoded DTMF signals, are supplied to the
microphone (e. g. of a telephone handset 120, or other
interfacing equipment). These acoustic signals are
converted by the microphone 118 of the handset 120 into
electrical signals which are supplied, via a local
telephone network, to a local telephone office 502. In
the illustrated embodiment, the local office 502 couples
the telephone handset 120 to a long distance carrier
switching center 512, via the 800 switch network if an
eight hundred number was initially dialed, or by a direct
access link if an inter-exchange code was received from
the auto-dialer 100. In this manner, the DTMF signals
output by the auto-dialer 100 are supplied to the carrier
switching center 512. If the initial dialing sequence
was preceded by an inter-exchange code (e.g., lOXXX), the
auto-dialer 100 will also transmit to the local office,
using standard DTMF tones the desired destination number
which the local office 502 will transmit to the long
distance carrier switching center as non-tone data.
The carrier switching center 512, in this
example, is responsible for decoding encoded DTMF
signals. Upon connection with the carrier switching
center 512, the auto-dialer 100 provides that data which
is required to complete the call, e.g., desired
destination number (if the call was preceded by an 800
connection), calling card and device ID information. The
output of the carrier switching center 512 is coupled,
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e.g., via a long distance network, to a destination local
telephone office 530 which, in turn, completes the
connection to the destination telephone represented by
the handset 534.
5 As illustrated in Fig. 7, the carrier switching
center 512, includes a DTMF tone to data converter
circuit 516 for converting the standard DTMF tone pairs
of the received DTMF signals into their corresponding
symbols/numbers. The carrier switching center 512 also
10 includes a non-tone demodulation circuit 514 for
monitoring alterable characteristics of the DTMF signal
being received by the switching center 512 and decoding
the encrypted information represented by the signal
characteristics being monitored. The non-tone
15 demodulation circuit 514 includes circuitry for
determining the system time to be used when decoding data
encoded as a function of a system clock 111. To perform
the processing and description of the received signal,
the carrier switching center 512 includes a processor 518
20 coupled with the tone demodulation circuit 514, a DTMF
tone to data converter circuit 516 and a database 526.
The data base 526 contains, e.g., information concerning
the body number or device identification number of valid
auto-dialers 100, a billing database and, e.g., other
25 information relating to the user or the particular
encoding scheme used by each auto-dialer 100 listed in
its data base 522. The processor 518 operates to control
the carrier switching center 512 to perform the functions
described above in regard to Fig. 6. performed by the
30 carrier switch.
While the encryption of data into a DTMF signal
by using different characteristics, e.g., tone duration,
to represent data has been described above, it is also
possible to encode data into a DTMF signal by sending
35 signal tones as opposed to a tone pair which would
constitute a valid DTMF tone. As discussed above, unless
a low tone and a high tone are received simultaneously
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for a minimum period of time a standard DTMF detector
will not acknowledge receipt of a valid DTMF tone and
will normally ignore the single tone being received.
In accordance with one embodiment of the
.._ present invention single tones, e.g., either a low tone
or a high tone, are used to transmit data. In such an
embodiment, each low tone and high tone used,
individually, to transmit data is associated with a
particular data element, e.g., a letter, numeral or word.
To transmit the information, e.g., data element
associated with the single tone, the tone is sent without
a corresponding high or low tone being asserted. Thus, a
standard DTMF decoder circuit receiving the single tone
will ignore it, e.g., as an error. However, a decoder
circuit according to the present invention detects the
receipt of a single tone and uses a look-up table, as
described above with regard to using signal
characteristics to represent information, to interpret
the encoded data, e.g., the data represented by the
single tone. In addition to the frequency of the single
tone, the various characteristics of the single tone,
e.g., it duration, amplitude, etc., may also be used to
represent data as described above.
In yet another embodiment, tones which are
outside the range of a standard DTMF detector circuit,
but within the passband of the filters used to filter
either the high or low tone DTMF signals received by a
detector circuit are used in a similar manner to transmit
data.
Accordingly, by using high and/or low tones
that are outside the range for standard high or low tones
used for DTMF signals, it is possible to encode data into
a DTMF signal by asserting such tones during the
interdigit period or at the same time a DTMF tone pair is
being asserted, e.g., as a third tong, without affecting
the ability of a standard DTMF detector to detect the
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DTMF tone pair. In this manner, the amount of data that
can be transmitted along with a DTMF signal can be
greatly increased without effecting the ability to detect
the tone pairs of the DTMF signal.
B. Limited Access to the Data Stored in the Memory
of the Auto-dialer
In addition to the data encoding/encryption
features described above, the auto-dialer 100 of the
present invention contains several additional features
which are designed to further enhance security. These
additional security features which are described below
may be used alone or in conjunction with the DTMF
encoding scheme of the present invention.
As discussed above, the auto-dialer 100 of the
present invention is programmable and may be programmed
with a host of different types of information relating
to, e.g., DTMF tone output levels and/or the tone output
frequencies required for satisfactory performance,
calibration parameters for adjusting the output of the
auto-dialer 100 to achieve specific output signal levels
and/or frequencies, a list of standard DTMF and non-
standard DTMF signals (tone pairs which are not included
in the set of 16 standard tone pairs) the device can
generate and/or recognize.
In addition to this information, the device may
be programmed to store data representing carrier access
codes, the user's selected personal list of destination
phone numbers, personal identification information and a
wide variety of other types of information that can be
stored in the device ROM 106 or RAM 108.
As will be described further below, the
personal identification information stored in the device
may also include voice recognition data. This voice
recognition data, e.g., voice pattern information
associated with the authorized user of the auto dialer
100 may be supplied to a system (either local or remote)
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which is capable of comparing the stored voice
recognition data to a live voice sample received from a
user in response to a prompt, e.g., audio prompt. By
storing the voice characteristics within the auto-dialer
100, the possibility of using voice recognition is vastly
-_ increased due to the diminished requirement of a
centrally storage facility for such records, and the
interconnection of the storage facility with each of the
many places where voice recognition might be useful. One
should also note that the requirements for a higher
degree of certainty with regard to voice recognition are
greatly reduced when the voice being compared is already
reasonably verified by virtue of the person's possession
of the auto-dialer 100, as opposed to when there is no
basis for any presumption such as when one stores the
voice file in a common database that the person being
tested is the authorized person.
Because the auto -dialer 100 can be programmed
remotely, the auto-dialer 100 permits the remote
alteration of a pre-determined sequence or tone strings
which are stored in memory for use as an identification
code for initiating telecommunications connection upon
the receipt of a predetermined group of tones.
It is also possible to program the auto-dialer
100 to interject a pre-programmed and remotely alterable
timing space between a string of tones such that the
spacing conforms to a predetermined amount of time
necessary for one call switching system to alter its
conventional processing protocol or make contact with
another and that the second or subsequent tone-strings
will not begin to be de-toned until such pre-determined
amount of time necessary for the switching system to make
- the anticipated transition and that the second or
subsequent tone-strings will not begin to be de-toned
until such pre-determined time has elapsed, and where the
first string (e.g., access code, sequence) is stored in
memory independently of the data which is subsequently
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transmitted to the second or subsequent call-processing
system, and that the first access string is not within
the control of the user. Further, it is possible to
program the auto-dialer 100 to transmit indexed data at
only certain points in a call sequence.
As will be discussed further below, the auto-
dialer 100, via the processor 104, ROM 105 and RAM 108,
permits the storage of data relating to constraints
associated with the access or use level which is to be
afforded to an auto-dialer's authorized user. Such
constraints might include overseas calling restrictions,
ATM withdrawal restrictions, restrictions relating to the
use of other systems, functions, or programs which are
accessible by use of the auto-dialer 100. These
constraints may be changed by re-programming the auto-
dialer 100 from, e.g., a remote source.
In order to prevent the unauthorized access to
the information stored in the auto-dialer 100, in one
embodiment, a user is limited in the degree of access the
user has to the information stored in the auto-dialer
100.
The amount of access a user is given to the
various types of stored information in the auto-dialer
100 is determined as a function of the data's
sensitivity. For example, in one embodiment, a user is
given full access to his/her list of personally-selected
destination telephone numbers with the ability to
reprogram these numbers at will. However, a user is
denied complete access to device identification number
information and other device security information (e. g.,
system clock settings).
In another embodiment, entry of PINs, e.g.,
three PINS, in conjunction with a randomly selected group
of words, e.g., three words, associated with the PINS
(referred to as "PINWORDS") is required before a user is
allowed to reprogram or access certain other data (e. g.
user device preferences such as language preference,
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mailing address, etc.).
Furthermore, for business reasons, in some
cases, it is desirable to restrict a user from changing
__ the default calling services so that, e.g., the user can
5 not change the default carrier access number, or related
billing data stored in the auto-dialer 100.
While the device body number, billing
information and identification number of various calling
services which may be contacted using the auto-dialer
10 100, may be programmed into the auto-dialer 100 at the
factory before supplying the device to the end user, in
many cases it may be desirable to subsequently alter this
information as well as the other information, e.g.,
calibration information, stored in the auto -dialer 100.
15 However, as with access to the information contained in
the device, it is desirable to limit a user's ability to
re-program certain portions of the information stored in
auto-dialer 100.
Accordingly, in one embodiment of the present
20 invention, the auto-dialer 100 can be reprogrammed by
signaling the auto-dialer 100 via a series of acoustic
tonos, e.g., a pre-selected series of tones stored in the
RAM 108 or ROM 106, to perform various operations such as
to store data or to replace data in memory with new data.
25 In accordance with the described embodiment, in
order to prevent the unauthorized reprogramming of the
auto-dialer 100, a particular signal, e.g., a series of
DTMF tones or encoded DTMF tones stored in its memory
(ROM 106, RAM 108), must first be received before the
30 device will enter a controlled-access mode in which
information RAM 108 which cannot normally be altered is
~ permitted to be reprogrammed, i.e., changed. The stored
series of tones which, when received and decoded by the
auto-dialer 100, are used to cause the auto-dialer 100 to
35 enter the controlled access mode may, optionally include
a pre-programmed unique device number which is only used
as a security key in the re-programming process or as the
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basis of an encryption of an outgoing tone-string from
the auto-dialer 100.
In the described embodiment, received signals
are compared to authorization codes or "keys," taking the
form, e.g., a string of tones, stored in memory to
determine whether the person or system attempting to
reprogram the auto-dialer 100 has the authority to do so.
If a match is made between a received signal and an
authorization code stored in the auto-dialer 100 the
reprogramming tone-group and the pre-established
operations and/or degrees of use permitted by the
received authorization code are allowed, i.e., enabled.
However, if an authorization code is not received, only
the normal, limited access to the data and normal degree
of programmability is permitted, e.g., a user is allowed
to program the auto-dialer 100 with new additions or
changes to his/her personal phone list, but not access or
alter the calling card identification information stored
within the device.
Accordingly, in one embodiment, the auto-dialer
100 permits the alteration of, e.g., a string of network
access codes, dialing sequences and related protocols,
stored in the RAM 108 which are used in the initiation
of, e.g., a telephone call, upon the receipt of a
remotely generated, pre-defined string of tones which are
used to enable the alteration.
Various signals, e.g., acoustic, electrical,
etc., that serve as "keys" may be required to alter, or
re-program, the various types of data stored in the RAM
108 and/or enable/disable functions which can be accessed
by the user. These signal "keys" may be any type of
signal that the auto-dialer 100 can recognize, either
standard DTMF signals, encoded DTMF signals, non-DTMF
signals or, simply a sequence of signals generated by the
proper manipulation of the keys of the input device 105.
Alternatively, the desired recognition of certain encoded
data may only be permitted if the data is received
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through a pre-defined input of the auto-dialer 100.
Further, so as to prevent unauthorized access
and programming to various functional or storage areas of
_ the device, the sequence of tones or signals required to
perform such changes may be a function of the system-
clock, the non-transmitted identifier held within the
auto-dialer 100, the identifier of the system seeking to
program the auto-dialer 100, a mathematical result based
on two or more values stored in either the auto-dialer's
memory or the device seeking to perform such changes, or
any combination of these or other factors.
Accordingly, the auto-dialer 100 can receive
and decode pre-selected and/or remotely alterable tore
pairs, e.g., DTMF signals, as a "key" to place the auto-
dialer 100 in a mode which may not be otherwise
accessible to the user through the manipulation of keys
on the auto-dialer 100.
The auto-dialer 100 is designed to permit
various remote services to change various aspects of the
auto-dialer 100 by changing the contents of particular
locations within the auto-dialer's RAM 108. Therefore, a
sexies of keys are recognized by the auto-dialer 100,
with each key providing access to a limited portion of
the device functionality and memory. For example, a
first tele-communications manager may have the authority,
and a first key required to alter the contents of a first
memory location containing a calling pattern stored in
the first auto dialer memory location. The first key
provided to the first tele-communications manager allows
the first communications manager to alter only the
contents of the first memory location. However, it does
not enable the alteration of other memory locations,
e.g., the containing debit account information which may
be altered, e.g., by using a second key.
In addition to reprogramming the auto-dialer
100, the degree of functionality a user is permitted may
also be altered or reprogrammed in response to the
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receipt of various signals. For example, when an
unauthorized user attempts to use an auto-dialer 100
which is reported stolen, a signal, e.g., an acoustic
signal may be sent over the phone which when received,
causes the auto-dialer 100 to deactivate itself. In such
an embodiment, the user is unable to reactivate the auto-
dialer 100 without assistance from a central service
office. Similarly, an acoustic signal from a central
service that can be provided via, e.g., a telephone, may
be required to initialize devices shipped to a user or to
reactivate a de-activated device.
Thus, the auto-dialer 100 permits the
activation/suppression of features, attributes or other
operating parameters stored in the ROM 106 or RAM 108, on
a selective basis controlled by the initial
calibration/programming procedure, and alterable through
the receipt of remotely generated, pre-established, and
remotely alterable tone pairs which may be used as keys
to enable/disable certain functions such as memory
location access and programmability. It also provides
for the capability for the auto-dialer 100 to cease
functionality, or have limited functionality, upon
receiving a predetermined set of tones and to resume less
restricted functionality or, alternatively, more
restricted functionality upon the receipt of
predetermined tones from an outside source. Furthermore,
in one embodiment, the keys on the auto-dialer 100 cannot
be used to alter the functionality of the auto-dialer
100, except as permitted by the privileges currently
defined by control parameters stored in the RAM 108 OR
RAM 108.
Because the auto-dialer 100 of the present
invention is designed to be acoustically coupled to a
phone or other device capable of acoustically coupling
with the device, e.g., calibration equipment, ATM
equipment accord~,,.~ to the present invention, etc., the
signals which serve to enable the reprogramming of the
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auto-dialer 100 and to thereafter reprogram the auto-
dialer 100 may be received, e.g., from a local device
capable of creating appropriate signals, or,
_ alternatively, from a telephone coupled to a remote
center which is responsible for the programming and/or
- calibration of the auto-dialer devices 100 of the present
invention.
Because the auto-dialer 100 can be easily
programmed or reprogrammed from remote locations, e.g.,
via the use of a standard telephone coupled to a computer
located at a central office or from locally enabled
equipment, the auto-dialers 100 can be shipped to
consumers without being programmed with any sensitive
data, e.g., calling card numbers, credit card numbers,
account number and balance information, etc., which is
important to keep from unauthorized individuals because
of security concerns.
In accordance with the present invention, a
consumer, upon receiving an auto-dialer 100 which has not
been programmed with user-related data, can call a
central service which can initialize the auto-dialer 100
with the user related data by programming the auto-dialer
100 via an acoustic coupling to e.g., standard telephone
lines, following the receipt of identification
information only known by the authorized user and the
central service. The information and data programmed
into the auto-dialer 100, at the time of initialization,
may include the calling card number and other account
information which was not previously programmed into the
auto-dialer 100 because of security concerns.
Alternatively, if it is desirable to send the
auto-dialer 100 to the user fully programmed and enabled,
the device can be placed into a "locked" mode which the
user can unlock by selecting the predefined PIN in
association with a device-prompted PIN word or upon the
receipt by the auto-dialer 100 of a voice sample which
was supplied at the time the order for the auto-dialer
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100 was placed. Both of these security aspects are
described below.
In either case, the auto-dialer 100, when in
transit to the user, remains of little or no value to
5 anyone other than its authorized recipient who is the
only person with the information required to activate the
auto-dialer 100.
C. Security Schemes and Methods
10 Because the auto-dialer 100 of the present
invention is programmable, it may be programmed to
support a wide variety of security schemes and to perform
a wide variety of data storage functions. Discussed
below are a few of the many possible security features
15 that are incorporated into the various embodiments of the
auto-dialer 100.
As discussed above, the auto-dialer 100 of the
present invention incorporates a system clock. In one
embodiment of the present invention, this system clock is
20 used to provide a seed number to a pseudo random number
generator. The output of the pseudo random number
generator is used in various data security schemes as
will be described below.
In accordance with one embodiment of the
25 present invention, the pseudo random number generator,
is used as a basis for encoding data into DTMF tones in a
time sensitive manner, e.g., the data table used to
encode data may change as a function of the pseudo random
number generated using the system clock contained in the
30 auto-dialer 100.
Because the present invention provides for the
calibration of the system clock prior to shipment to the
customer and/or subsequent to shipment from a remote
location via signals transmitted to and from the auto-
35 dialer 100, the accuracy of the system clock can be
maintained to a relatively high degree of accuracy even
when inexpensive clock circuitry is used. The high
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degree of accuracy is achieved by storing in the RAM of
the autodialer 100, at the time of setting of the system
clock, or subsequent resetting, the precise time and date
of the setting or resetting, as the case may be. At a
subsequent time, the current clock setting is analyzed in
-- relation to the precise moment when the clock was last
set, providing an indication of the actual deviation of
clock counts that the clock being calibrated varies from
the standard. By adjusting the number of counts which
represent a moment of time, based on the actual deviation
of the current clock over the spanned interval by, e.g.,
altering a system clock control parameter in the RAM 108,
one can achieve a very high degree of accuracy from the
otherwise linear system clock circuit, and accomplish
such accuracy without the need for more expensive
components.
The system clock precision that can be achieved
in this manner permits the pseudo random number
generation scheme used in each auto-dialer 100 to be
consistent with other similarly programmed devices and
interfacing equipment, insuring a predictable outcome
from the auto-dialer's pseudo random number generator at
any give time, which enables the recognition and decoding
of data encoded by the auto-dialer 100 by other similarly
programmed devices.
In one embodiment, the auto-dialer 100
increases the level of difficulty associated with the
unauthorized decoding of information encoded in a
generated DTMF signal by inserting meaningless data into
the data stream representing additional filler data which
has no information significance.
The locations in the data stream at which this
filler information is inserted is a function of the auto-
dialer's pseudo random number generator 113. It may also
be a function of other data relating to the device
identification, the current function of the auto-dialer
100 and/or other characteristics of the auto-dialer 100,
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e.g., battery voltage.
As the system clock 111 in all auto-dialers 100
and switching offices capable of decoding encoded DTMF
signals referred to as "enabled switching offices" share
the same seed number at any moment in time, the location
of the filler and real data can be predicted by the
switching office which can then extract encoded data
based on the current, time-sensitive encryption.
The central service center to which the
telephone call is routed can determine the time the call
was received and use that information in conjunction with
the information about the pseudo random number generator
and data placement scheme implemented by the auto-dialer
100. It can then use this information to distinguish
between the filler data and the relevant data encoded
into the received DTMF data stream.
To insure, that the central office can
determine that embedded data has been decoded properly
and to provide error correcting capability, check bytes
are included in the encoded data. If the central office
fails to decode the encoded data correctly using the
predicted output of the pseudo random number generator,
in one embodiment, it attempts to decode the data using
the preceding and/or subsequent output of the pseudo
random number generator. In this manner, the central
office can accurately decode information which was
transmitted in one system clock period and received in
one or more adjacent period. Furthermore, minor errors
in the system clock will note prevent decoding of
encrypted data.
Thus, as described above, to minimize the
effect of the system clock errors, the switching office
may apply earlier and/or next valid check sums or other
tests before, e.g., dropping the call. In the event that
this additional latitude is provided, and the data is
found to be intelligible, the caller may receive voice
instructions to send an additional dynamically-based
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string of data which provides other data relating to the
function of the auto-dialer. If the enabled switching
office computer determines remote transmissions are, in
_ fact, coming from an otherwise-active auto-dialer 100,
perhaps after checking with its database, the user may be
-_ provided with a voice prompt which will guide the user
through a recalibration of the device's system clock.
Accordingly, because of the regular scrutiny of
incoming data, the enabled switching office receiving the
signal from the auto-dialer 100 will be able to detect
the difference between valid information and meanir.Jless
filler information while a person recording the telephone
transaction may not be able to do so.
In accordance with still another embodiment of
the present invention, after making a connection to an
enabled switching office, the auto-dialer 100 transmits,
using a series of DTMF tones or other tones which may or
may not be encoded, additional data intended to be used,
e.g., by the central telephone switching office. This
data may include, e.g., additional billing information
not encoded into the telephone number or other device
identification information.- The provision of this
additional security information may occur only
occasionally, either a result of system-timing, a
particular desired function, or a computed check-sum
based on the transmitted data.
As discussed above, with regard to the use of
the system clock and random number generator for
controlling the placement of filler data into data
encoded into the destination number, the same method of
placing filler data into the signals being transmitted to
the enhanced switching office after the telephone number
_ is sent may also be used. The enhanced switching office
will be able to distinguish this filler data from the
actual information data in the manner previously
described.
The use of the system clock 111 may also be
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incorporated into the reprogramming of the auto-dialer
100 by using the derived pseudo-random number in
conjunction with other data stored in the auto-dialer
100. Unless the auto-dialer 100 receives those pre-
y established values required to program certain aspects of
the auto-dialer 100, and those values were modified in
correct coordination of the current system-clock 111 of
the auto-dialer 100, the auto-dialer 100 will reject such
instructions.
In one particular embodiment, the auto-dialer
100, except during those programming periods when the
user is programming a speed dial list, which can only
occur following the correct selection of a PIN, is
specifically designed not to display any phone number
used for access purposes by the auto-dialer 100. When
making a speed dial call, under certain circumstances, an
alternate number is shown on the display device 202.
However, this access number, when dialed manually, will
permit the use of the auto-dialer 100 in its enhanced
mode, and, by disregarding those digits which are emitted
by the auto-dialer 100 which relate to the first access
data (e.g., to the non-enhanced-local office), permit the
user to make full use of the auto-dialer 100.
D. Using The System Clock In Conjunction With A
Plurality of Stored Access Numbers
While some unauthorized users gain access to
calling card number information through monitoring
telephone calls being placed by authorized users, others,
known as hackers, attempt to gain improper access to
private phone networks and other telephone accessible
facilities (e. g., data centers), by a trial and error
method. In accordance with such a method, a hacker
attempts to place a call using a computer which generates
calls to, e.g., a long distance service carrier or
another target system such as a database and then enters
a calling card number. Following connection to the
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target, upon request for a password or other authorizing
group of symbols or numbers, e.g., a calling card number,
the hacker directs his/her computer to generate a
_ sequence, e.g., a randomly selected sequence, of DTMF
5 signals or other signals to simulate the signals which an
-- authorized user would provide. In the event that the
sequence is not recognized by the target, the call is
dropped by the target. The hacker's computer, when it
receives a signal indicating that the call has been
10 dropped, automatically re-tries the access number and
attempts to gain access using a different numeric
sequence or signal often thousands of times, thousands of
calls. Accordingly, thousands of calls may be placed
before unauthorized access is achieved in this manner.
15 As one can assume that any facility which incorporates a
password or authorizing group of symbols was designed for
access by authorized persons only, and each call-attempt
by a hacker or other unauthorized person or computer to
gain access to the target system blocks one port of entry
20 for authorized users, it is desirable to develop a means
of eliminating the potential for such activity.
While using lengthy calling card numbers, and
thus the number of possible numbers, increases the number
of calls required, on average, by a hacker before the
25 hacker will discover a valid calling card number, the
target (e. g., long distance service carrier) is still
confronted with the problem of responding to the numerous
nuisance calls generated by the hackers.
In one embodiment of the present invention, the
30 auto-dialer 100 is used to store a plurality of telephone
access numbers for the same long distance service or
carrier. The particular access number that the auto-
_ dialer 100 will select is a function of the output of the
system clock and a preselected pseudo random sequence
35 that is used to determine which number for the long
distance carrier is active at any given time.
The service to which the call is directed, for
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its part, will selectively respond, i.e., answer calls
made to the telephone number which is active at that
moment in time. Calls made to inactive numbers will be
traced to their source to identify hackers or will be
S otherwise blocked from accessing any system protected by
the enabled switching office.
Thus, in this embodiment, the auto-dialer 100
dials only the particular access number which is active
at that moment. However, a hacker will be confronted
with the possibility of now having to dial multiple
numbers before even reaching an active telephone line of,
e.g., a long distance carrier.
Using the above scheme in combination with the
auto-dialer 100 of the present invention, can greatly
reduce a long distance carrier's burden of responding to
calls placed by hackers attempting to gain access to the
long distance carrier service while placing no additional
burden on the authorized user who is attempting to place
a call using the auto-dialer 100. Furthermore, because
the origin phone number is often included within the data
exchanged by the local office with all subsequent
switching facilities including the station assigned to
the destination phone number used for the placement of a
call, it provides a method by which hackers can be
readily identified for referral to appropriate law
enforcement organizations.
Accordingly, the above-described method of
altering the active telephone numbers a long distance
carrier responds to on a pseudo random basis offers
potential cost savings by decreasing the effort a carrier
service must take to respond to hackers and by decreasing
the chances that a hacker will be able to obtain a valid
calling card number through the use of the above-
described trial and error method.
The response of a carrier service or switching
center made to an active number will now be described in
greater detail. While the process described below can be
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executed in various scenarios, the example provided here
assumes that a carrier service or switching center is
providing calling-party screening services for multitude
of facilities.
When a call comes in on the currently active
.- access number, the carrier service or switching center
receiving the call will, after providing a voice or data
prompt to the calling party, and receiving from the
user's auto-dialer 100 the string of data that follows,
decode the data, e.g., in accordance to the system-clock-
based encoding method valid at that moment, to determine
which restricted-access facility or function (the target)
the caller is intending to contact or utilize. The
switching center also determines the identity of the
auto-dialer 100 being used to place the call from the
received data. As an option, the switching facility then
initiates, using a separate line, a data inquiry to the
target to determine if it will accept the user identified
by the particular device number, and, if appropriate, the
origin phone number of the requesting user.
The inquiry to the target may not include the
origination phone number of the device/user making the
request to access the target, and the target system may
or may not verify the appropriateness of the origination
phone number as an eligible origination point for the
particular user/device. Alternatively, if a lower level
of security is desirable, once the device data has been
properly decoded, and the desired facility is determined
by the enabled switch, the call is transferred without
prior approval of the target system.
If the target determines that the requesting
user/device should be granted access to the limited
access facility, e.g., based upon its examination of the
data provided by the switching center, as well as other
data which may be stored within the target system, the
switching center transfers the call to the target.
This same scenario can be applied to the
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calling card industry where unauthorized users apply the
same methods to achieve long-distance theft by repeatedly
trying various account numbers until one is accepted by
the carrier for the placement of long distance calls.
In this scenario, the auto-dialer 100 will
generate those tones which represent the only currently
active access number for the long distance carrier. If
the unauthorized user dials an inactive access number,
the long-distance carrier can note the originating phone
number of the caller without allocating switching and
data-base retrieval resources to the call.
In addition to the above scheme for using
varying access numbers to, e.g., a long distance carrier,
in another embodiment, the auto-dialer 100 selects
various access numbers to the same particular carrier
service or switch system from a list stored in its memory
according to a usage based numerical sequence stored in
the RAM 108. The numerical sequence is incremented by
the processor 104 each time the auto-dialer 100 is used,
e.g., to contact the particular long distance carrier.
In such an embodiment, the receiver, e.g. particular long
distance carrier, stores the usage infornlation about
each access-authorized auto-dialer 100 and the numerical
sequencing system in each authorized auto-dialer 100.
For example, as part of a call transaction, in
such an embodiment, the auto-dialer 100 transmits a usage
based incrementing indicator based on the numerical
sequence, with other data, e.g., the auto-dialer's body
number, an account number, the desired destination number
etc.
The received indicator is compared by the
central database against the last such information which
was received from the particular autodialer 100 to
determine if: 1) the indicator has been incremented as
expected, thus indicating that a valid device had
initiated the call, or 2) the indicator has not been
incremented indicating that a valid device had not
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initiated the call. Upon determination that the data has
not incremented properly since last contact, the desired
activity, e.g. placement of a call is refused.
The systems described above to provide greater
access security can be incorporated into computerized
:_ communications equipment, e.g., modems and other
equipment designed to provide communications interfaces
between, e.g., computers. In this embodiment, the system
clock 111, its operating algorithm and other basic
hardware instructions, are incorporated into the embedded
processor of the modem or remote interface equipment,
while other user-related software is made part of the
communications software of the computer. The modem is
shipped without any setting or calibration of its system,
clock.
Following installation of the enhanced modem
referred to above, to make contact with a target database
or computer system which is protected by the screening
protocol described above, the user provides data to the
software which will cause the target database or system
to recognize the user (e.g. user name, address, user #,
etc.) Upon completion of these entries, the modem dials
a single phone number which terminates at the modem
initiation system which will, once approval has been
achieved, provide one or more access numbers to enable
future connections with target systems through the
designated enhanced switching system.
Upon connection, the initializing system sends
to the remote system a series of tones which the remote
system, if properly enabled, responds to in a dynamic
fashion so as to indicate to the initializing system that
the remote system is using the appropriate protocols and
is enabled with the correct system-time settings. The
remote system then transmits, following the receipt of
predetermined codes, certain values contained in its
embedded controller of the modem (e. g. its publicly-
transmittable identity) and some or all of the data which
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the user entered into the communications software,
including an indicator of the target databases) for
which the initializing service provides screening-access
services and the user wishes to contact in the future.
5 For each target database which the requesting
user is seeking to gain access, the enhanced switching
system queries the target database to determine if the
requesting user is eligible, at this time, to gain access
into the target database.
10 If at least one of the targets for which
screening services authorizes access, the enhanced
switching system transmits to the embedded controller of
the remote modem an instruction, to enable its system-
clock according to the current system standard time, and
15 records such time followed by those access numbers which
will be used in the future as well as the identifiers for
each of the targets which the user has been authorized to
access.
Upon authorization by each target databases)
20 to permit the user access, the enhanced switching system
transmits to each authorizing target the publicly-
transmittable identity of the now-authorized modem),
which then records the received value to the user's
record. Future requests to the target for access by the
25 user, through the enhanced access system, will be based
on this value. During the first month, the enhanced
switching system monitors the progress of the system-
time, and after a preselected number of days have past
since the initial setting of the system-clock, the
30 enhanced switching system provides that data which is
required to calibrate the system-clock.
If a target database determines, either upon
first request or subsequently, that the user is not
eligible to gain access, the target database or system
35 informs the enhanced switching system of its findings.
The enhanced switching system can then transmit to the
enhanced modem and its related communications software
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that entry has been denied. If the key number for the
target has been supplied earlier, the enhanced switching
system sends a command to disable its future use. If
there are no other target systems with which the user is
eligible to access through the enhanced switching system,
:_ the access number file and the system-clock are also
disabled.
Once properly installed and access to a target
system has been enabled, it is desirable to minimize the
value of the unauthorized removal of the modem from the
computer, the data relating to the system-time is stored
in electrically-dynamic memory within the embedded
processor. Thus, upon the removal of the electricity
required to sustain the data, any information stored in
the memory is erased irretrievably. The alternate source
of power to be used to maintain this data when the
computer's power supply is not available is located on
the opposite side of board from the embedded controller.
An electrical connection among the alternate power supply
and the embedded controller is provided by the copper
connections of an unused, u-shaped connector within the
slot of the mother board: Upon the removal of the modem
from the motherboard, the data held in the embedded
controller is discharged.
Additional methods of guarding against improper
access to remote databases and data contained within the
auto-dialer 100 may be accomplished by the use of voice
recognition, other means of biometric identification, and
the use of rotating PINS. Such additional security
methods are discussed in detail below.
E. Voice Recognition and Other Means of Hiometric
- Identification
In addition to the above described security
features, the present invention can incorporate voice
recognition features for added security and/or
convenience. As described above, the auto-dialer 100 is
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responsive to acoustic signals to perform various
operations including the enablement of various functions.
In accordance with one embodiment of the
present invention, information concerning one or more
characteristics of an authorized user's voice is stored
in the RAM 108. This voice information is of a type
suitable for doing voice comparisons, e.g., it may
represent a recorded voice pattern of the authorized user
of the auto-dialer 100 when the user is saying a certain
word or phrase. Alternatively, the auto-dialer 100 can
store a string of data which interfacing equipment may
use to access a user's data file. The voice
characteristic data stored in the auto-dialer 100 may be
obtained from a central office which analyzes the user's
voice pattern, and then converts the pattern, or an
aspect thereof, into digital data, which is then
transferred and stored in the auto-dialer 100 in the same
manner that other data is programmed into the RAM 108.
Because the ability to reprogram the RAM 108
may be limited, e.g., by a requirement that a stored pre-
selected sequence of tones be received before allowing
reprogramming of the RAM 108, the auto-dialer 100 can
serve as a secure, portable, library for the voice
identification stored therein.
The auto-dialer 100 may be used as a secure
source of other identification information as well, e.g.,
height, weight, eye color, etc.
The auto-dialer 100 described above has several
features that make auto-dialer 100 useful for
implementing a voice based identification system. First,
storage of a user's voice file in the auto-dialer 100,
with the auto-dialer ability to subsequently transmit it
quickly, eliminates the need for searching a data base
for the user's voice file. As it is impractical for a
voice recognition to search all files to determine which
one is the caller on the line, the first step in this
process must be to access the applicable voice data file
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to base a voice comparison.
The storage of a person's voice or other
biometric information in an auto-dialer 100 can
substantially speed the successful use of voice
recognition systems. First, because of its use of
-_ indexed tones, the auto-dialer 100 is capable of
transferring data quickly, the auto-dialer 100 can
provide voice processing equipment with the user's stored
voice characteristic data file in very little time.
As referred to above, when the particular data
file used for voice comparison is selected based solely
on information provided by the person seeking access to
the system, it is important to be discriminating when the
voice instructions are analyzed, assu~~ning that there is
no other means to guard against abuse (such as the person
having a physical object which is unique to him/her,
e.g., the auto-dialer 100,) that the switching system can
authenticate. As it is possible to record another's
voice without his her knowledge, the risk of unauthorized
access remains with voice processing systems, thus
requiring reasonably precise matching of the current
speech with the stored speech. Hy using the auto-dialer
100 to provide the voice file to the analyzing system,
there is much less risk of unauthorized access due to its
ability to provide a dynamic way of discriminating the
authorized user from the unauthorized user, permitting an
appropriate relaxation of voice recognition standards
which otherwise must be applied since the likelihood that
an impostor in possession of an auto-dialer 100 can
replicate even coarse qualities of the authorized user is
relatively small. In such a case, possession of the
. auto-dialer 100 serves as a degree of proof that the
person making the call is the authorized user.
Additionally, because the auto-dialer 100 is
designed to not block out ambient noise through the use
of barriers, the voice recognition system has the
opportunity to sample the ambient noise, during a
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deliberately interposed period of silence by the auto-
dialer 100, the voice recognition system is afforded the
opportunity to quantify the background noise and reflect
such ambient influences from those which are presented
when the user provides the voice sample to be analyzed.
Also, the auto-dialer 100 can also provide a pre-
established tone level at a particular point during its
transmission, e.g., a point based on the current system
time of the system clock, thereby providing the voice
system with a means to compensate for line and
microphone noise influences on the subsequent voice
samples.
A further reduction in the applied security
criteria can be achieved by the incorporation of the
concept of rotating voice PINS. In this embodiment of
the current invention, a multitude of voice prints, e.g.,
of the user's name, birth city, or favorite relative, are
recorded and placed in the memory of the auto-dialer 100,
and, on a rotating, random basis, the auto-dialer 100
transmits a different voice print to the speech
recognition system which is operating in conjunction with
the auto-dialer 100. These words serve as the basis for
validation of the user, thus perniitting all other
instructions by the user to be speaker independent. A
further advantage of this concept is that by the storage
of voice prints in a portable device, they can be used in
off-line applications, where there is no ability to
access a central database.
By incorporating these aspects of the current
invention, it is possible for a voice processing system
according to the present invention to safely relax the
matching requirements which it otherwise needs in order
to avoid unauthorized access, while improving the
achieved level of performance, e.g., system security.
Further, many of the voice-recognition systems
being installed today are designed for use by travelers,
requiring each system operator to either duplicate the
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voice processing system, with duplicative voice files in
each location, or to provide high-speed access from a
process-only facility to a central facility in which ali
- records are stored. The amount of data which is required
5 to be transmitted back and forth between the remote
switching center and the central authenticating system or
be duplicated at each of several locations for voice
based security system can be extensive. By quickly
obtaining the data needed to perform the analysis from an
10 auto-dialer 100 or other device in the user's possession,
the associated costs in time and money of transporting
the data and/or providing duplicated data storage
facilities is eliminated.
The cost of providing such data storage,
15 whether it be duplicated in each such voice processing
system or centralized can be significant, considering the
requirement that such systems be fault-tolerant, and,
usually requiring further redundancies. These costs are
eliminated in accordance with the present invention by
20 the storage of the user's voice file within the auto-
dialer 100, where the cost of including sufficient
additional memory to hold the user's voice characteristic
file, when compared to the cost of either centralized
storage or the cost of providing duplicative storage in a
25 multitude of locations, is relatively insignificant.
Furthermore, to the extent that the cost of providing
voice processing is in direct relation to the time needed
to complete the process (authenticate or drop a call-),
the reduction in the time required to complete the
30 request, e.g., obtain the required voice characteristic
data is important.
Thus, the use of auto-dialer 100 for the
storage of user speech data for voice processing and
verification provides substantial opportunity to improve
35 voice verification systems and to substantially reduce
the cost of voice verification systems. Additionally,
there are numerous applications where speech recognition
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systems would be useful, e.g., immigration
identification, facility access control, etc., but the
high current costs, slow process and high number of false
negatives, e.g., when an authorized user is not
recognized by the analyzing equipment due to high level
criteria or false-positives, e.g., when an unauthorized
user is authenticated due to low level criteria make
these systems unattractive alternatives. Equipping
persons with a portable means to provide the necessary
data would make possible off-line speech verification
systems, without affecting its ability to operate with
on-line systems, with greatly improved performance and
significantly lower operating and capital costs.
In accordance with one embodiment of the
present invention, the autodialer is used to store and
supply biometric information to an access control device
used for controlling access to a system, e.g., a
telephone system, building, etc. Referring now to Fig.
14, and access control device according to the present
invention is illustrated.
As illustrated the access control device 900
includes an input device 903, e.g., a microphone, which
is coupled to a decoder circuit 907 for decoding
encrypted information, e.g., encoded DTMF tones, received
via the input device. The output of the decoder 907 is
coupled to a microprocessor 911 which is programmed to
control the operation of the access control device 900.
In this manner, the microprocessor 911 can receive
biometric information or live samples of biometric
identification via the input device 903 and decoder 907.
The microprocessor 911 is also coupled to an
encoder 905 which is capable of encoding commands and
data output by the microprocessor 911, e.g., into encoded
DTMF tones. An output of the encoder 905 is coupled to
the input of an output device 901, e.g., a speaker for
outputing the commands and other information generated by
the microprocessor 911.
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The microprocessor 911 is coupled to a
comparator 913 which is used to compare biometric
identification received from a portable information
storage device, e.g., and autodialer 100, and to compare
it to a live sample of biometric identification
information to determine if there is a match. If the
microprocessor determines, as a result of the comparator
operation, that the identification information received
from the portable storage device matches the live sample,
the microprocessor 911 enables an access control switch
909 to grant the individual seeking access to the system
the requested access. Otherwise, access is denied.
A description of the process involved in the
use of the auto-dialer 100 with voice recognition systems
follows. When a user of the auto-dialer 100 seeks access
to a secure network or facility, the network or facility
requests that the auto-dialer provide the voice
identification information recorded in the R.AM 108. This
information may be transmitted to the network or facility
by, e.g., a series of encoded DTMF tones.
To insure that it is the authorized user of the
auto-dialer 100 that is attempting to gain access to the
secure network or facility, the network or facility
requests a voice sample from the auto-dialer user. The
auto-dialer user may provide the "live" voice sample via
a conventional telephone handset microphone and telephone
network. The actual, received voice sample, is then
compared to the voice characteristic information received
from the auto-dialer 100.
If the actual, received voice sample matches
the received voice characteristics, the network or
service facility then gives the auto-dialer user access
to the requested service or facility. Otherwise, access
is denied and appropriate action can be taken with regard
to investigating and identifying the person attempting to
gain access to the network or facility.
In this manner, the auto-dialer 100, can be
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used in combination with separate voice recognition
circuitry provide at the network or facility which is
implementing the voice recognition security test, to
provide voice recognition capability without the need for
the network or facility implementing the test to store
voice characteristic data files on each person who is
authorized to access the network or facility.
The same process of storing voice-related data
into the auto-dialer 100 can be applied to other
biometric measures of a user including fingerprint(s),
retina or other eye-related characteristics, weight,
height, or graphical aspects of a user's body, e.g.,
face, hand, etc. As each of the aspect can be assigned
to a different protocol function of the auto-dialer 100,
it is possible for the auto-dialer 100 to accommodate
different security methods for different applications.
For example, in over the phone access applications, voice
technology may be most appropriate. In other access
applications where the user is present, it may be
appropriate to use one or more of the biometrics measure
describing an aspect of the user. The selection of which
data-description of the user is to be provided is based
upon the auto-dialer programming of the function selected
which is a matter of design choice that may be varied as
appropriate depending on the security application. In
the event of a telephone based access to a long distance
carrier for the placement of a calling card call, the
auto-dialer 100 may be programmed to automatically
transmit the voice-related data among the data sent to
the carrier. Alternatively, if the auto-dialer 100 also
stored, for example, data describing a physical
characteristic of the user, i.e. a composite of
standardized features, when the auto-dialer was used to
initiate a call to emergency services, e.g., 911 calls,
the receiving station could quickly have some
approximation of the caller, thus facilitating assistance
if, for example, the person calling was a child who was
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being held against his/her will and only had a brief
moment to alert authorities.
In another embodiment of the auto-dialer 100 in
its use with voice call processing, the data which is
transmitted from the auto-dialer 100 would include key
-- words (and their associated PINs) and data relating to
the user's speed dial list, but not include the user's
voice file. In this case, the switching office would
decode the data, and, if appropriate, prompt for a speech
or keyboard entry of the associated PIN, and upon the
correct entry, permit the user to speak, on a speaker
independent basis, those commands which would be common
phrases (Call Home, Conference Call, etc.) and if the
data supplied by the auto-dialer 100 contained such
references with associated instructions i.e. destination
number, or the spoken instruction was a system stored
instruction e.g. conference call, the instruction would
be executed, i.e. call placed.
In this embodiment, the switching service
equipment would serve several functions. In addition to
extracting the key words, the related PINs, and the data
relating to the user's speed dial list, e.g., system-
recognized names such as John, Paul, as well as the
destination numbers, the system would also extract, if
available, data which relates to a dialect or language
table to be used in analyzing the incoming speech
commands from the particular caller.
By indexing dialects, and storing such words in
isolatable directories, the system is able to further
reduce the errors and or search time that may otherwise
occur. This embodiment also suggests that the selection
- of the phone number which the device dials in order to
make contact with the enhanced switching platform be
based on a look-up table which indicates which language
and dialect, if possible, is native to the caller. As
the switching service can receive the number information
prior to the connection with the caller, the receiving
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100
processing system is thus able to load that dictionary
which relates to the speaker, thus reducing the error
rate and or search time that may otherwise occur.
The advantages of this embodiment are numerous
over the current system of voice access calling. First,
it eliminates the need for voice dependent processing,
reduces the associated false negatives which commonly
occur with its use, and the added expense in both capital
and operating expenses, e.g., longer processing time
resulting in more ports being required to handle the same
number of users, associated with such processing.
Second, it maintains the security of the switching office
because the office has the option of requesting the entry
of one or more additional PINS, e.g., based on its voice
prompt to the user. Third, it reduces the amount of
memory needed in the auto-dialer 100 since there is no
need to store both the user's voice file and speed dial
list. Fourth, it enables the same speech recognition
equipment to be used in programming the auto-dialer 100,
thus increasing the ease and convenience by which the
auto-dialer 100 can be programmed or re-programmed,
Fifth, when the auto-dialer 100 is programmed to operate
in, e.g. a country where it is known that speech decoding
equipment has not yet been installed, the auto-dialer 100
can continue to be fully functional as a non-voice
controlled device. Sixth, it eliminates the need for one
or more databases to store the voice files of all
authorized users, thus vastly reducing the cost of
implementing voice processing, while providing its user-
perceived conveniences. Lastly, as the user's
instructions are not voice dependent, when new features
are added to the switching system of the present
invention, the user is able to access them, without the
requirement of recording a new voice instruction, thus
reducing costs, and increasing the likelihood that a user
will take advantage of them.
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As discussed above, in one embodiment, the data
which is generated by the auto-dialer 100 and decoded by
the switching service according to the present invention
is a function of the system-clock and random number
generator output, thus making a tape recording of the
_ autodialer's output unusable for more than a brief period
of time. Additional security methods may also be used
with either voice dependent or voice .independent
processing systems.
The first such method involves the storage of
the actual time of the voice sample or provided voice
instruction in the case of a voice independent use. As
it is practically impossible for a human to speak the
same phrase in the same amount of time, where time is
resolved by, e.g., 50,000 slices per second, the
repetition of a phrase within say 10 milliseconds would
clearly indicate a recording. As the voice to noise
ratio must be substantial, there should be no difficulty
in discerning the beginning of the speech pattern nor its
end.
As it is equally unlikely that a person can
speak the same word identically in each case, even a
cursory quantification of the incoming speech pattern
should be stored as to avoid possible tape recording. To
decrease the number of errors associated with the use of
such a system, the overall level not be the only signal
characteristic measured. Instead, it is recommended that
the frequency span of, e.g., 5 Hz, with the highest level
be quantified and stored. In the event of a repetition
of the level of the identical frequency span, one can
assume that a recording is in use.
The signal to noise ratio, by itself, may also
be used as a reasonable indicator of potential recording
as the level of a speaker's output will normally vary.
Whether the auto-dialer 100 is to enable access
to a speaker dependent or independent switching system
according to the present invention, the opportunity
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arises for new uses of voice independent speech
processing, particularly when the auto-dialer 100 is used
to segment language and dialects so as to reduce error
rates. For many marketing companies, having a single
world-wide access system is advantageous. Equipped with
the auto-dialer 100, a user might be able to say, e.g.,
the name of a device provider from anywhere in the world,
and be connected to the service providers nearest
location, with, e.g., the call being answered in the
native tongue of the caller, with the telephone
representative being able to have a screen-full of data
about the person placing the call in front of him when
answering.
Alternatively, it provides the opportunity for
the service provider, according to the present invention
the opportunity to be of further service to the customer
by handling information requests, e.g., a request to call
a particular individual. In those cases where the user's
identity has been reasonably verified, i.e., when calling
a bank to get balance information, providing a telephone
confirmation to the tax collectors regarding the filing
of an electronic tax return, the switching office can,
when the destination call is noted to require such
verification, require the user to provide one or more
PINS before connecting the call.
Another embodiment of the auto-dialer 100 is
designed for providing a non-portable means of
identifying a user and providing access to an switching
system. In this case, the auto-dialer 100 is a small
rectangular container which contains a similar processor
to that which is required to perform the same functions
as the auto-dialer 100 except that there is no display,
and no input controls. In accordance with such an
embodiment, the device has two ports, e.g., RJ11 inputs,
one leads to a telephone and the other leads to the wall.
The device is battery powered, though its power is fully
isolated from the telephone line.
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During use of the device according to such an
embodiment, the invention performs the following
functions: whenever the telephone goes off hook, it
awakens from a quiescent state and turns on its DTMF
detector so as to enable the circuit to sense a
-_ predetermined tone-set from the attached phone, e.g. **1.
Upon sensing this tone-set, it initiates a call to a
switching system according to the present invention,
using an access number, if appropriate, which will
provide the switching system with a pre-alert as to the
language and dialect of the user. Upon sensing the ready
state by the switching system, by its receipt of a DTMF
signal, it transmits the data, using the standard
transmission protocol (e. g. indexed DTMF, indexed non-
DTMF) relating to the user who was identified by the
device, including, as applicable, the voice file, the
speed dial list , and other appropriate information.
Upon the conclusion of its transmission, the device
resumes its quiescent state, awaiting an off-hook
condition which is not preceded by a ring voltage.
This embodiment includes the storage facility
and the ability to transmit different data for each
different person for more than one individual based on
their individual access number (e. g. **1, **2, etc.),
and, in a similar embodiment, can monitor and transmit
over a multitude of lines. Alternatively, the device can
be designed such that it would be centrally located and
be accessible by any phone connected to the same circuit.
As described above, the provision of calling-
individual information provides substantial opportunities
to enable voice command calling. Although each telephone
call carries with it the calling party phone number which
can be received by interfacing switching equipment, the
fact that a call came from one line does not indicate the
specific individual Taking the call. In many large
businesses, even when an individual is assigned a
telephone number, rarely, is an outgoing call carried on
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the same telephone line as might be assigned to the
individual. This is primarily due to the fact that most
businesses find that they require less lines than
telephones as rarely is everyone on the phone at the same
time. Because switching equipment can match an available
line to any requesting telephone, there is no need to
dedicate any particular line to a particular telephone.
In yet another embodiment, a receiver device
according to the present invention is mounted on the
phone line does not store any data, but, instead,
provides a receptacle for the auto-dialer 100, such that
the output of the auto-dialer 100 is focused into a
cavity which contains an interface (e. g. speaker,
microphone; light emitter, receiver). Additional
significant hardware contained in the receiver device
would includes a processor, and a DTMF detector. In use,
when the electrically coupled receiver device senses a
pre-defined combination of tones, e.g. *11, it provides a
signal, e.g., an acoustic or light based signal, to the
auto-dialer 100 to cause it to transmit, e.g., acoustic
or light signals, to the receiver or base device which,
in turn, converts the signals into the standard
transmission protocol established for this purpose.
While this receiver device, i.e., base unit
embodiment is designed accommodate one person, it
provides an easy way for an individual, perhaps, in an
office, to identify himself remotely, without the
necessity of having to duplicate the intelligent portion
of the auto-dialer 100 in order to provide the user with
the flexibility that the auto-dialer 100 can provide once
the data contained in the receiver device has been
transmitted, and, as appropriate, the user authenticated.
In the event that the receiver device is to be
used in conjunction with facility access, the interfacing
equipment can, if so enabled, provide a system-clock
based set of codes to the auto-dialer 100 which will
prompt the auto-dialer to respond, using a similarly
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system-clock based set of tones, e.g., indexed DTMF
tones, related to the particular set of biometric aspects
which the interfacing equipment has requested and may be
stored within the auto-dialer 100. The transmission of
such information may be based on the presence of
_ additional data in the receiver device which indicates
that the provision of this data to the particular
interfacing equipment is permitted, and thus, eliminate
the possibility that the receiver device will provide
such data to another, unauthorized interfacing device
which makes a request for such biometric data. In this
way, the interfacing access system will only receive such
biometric data when the receiver device has been
programmed to transmit the data to the particular access
system.
The use of voice and other biometric aspects of
a user can provide additional secure access methods and
convenience without the requirement that the user carry
multiple access cards or devices, while eliminating the
requirement that interfacing equipment store or access
data for each potential permitted individual.
Additionally, because the device requires a
system-clock coordinated program to install either a
voice sample or other biometric sample, and in some cases
knowledge of information held in each auto-dialer 100
which is never transmitted in any form or otherwise
available to the public, e.g., a device number or data
relating to a particular application, it is much less
unlikely that the corruption of this system will occur.
Finally, because the auto-dialer 100 can
transmit the biometric data to the interfacing equipment,
- and the person using the auto-dialer 100 is, in theory,
present at the time of the access request, there is a
reduced requirement as to the level of biometric file
detail which is needed for validating the access request,
or the scrutiny which must be applied to the infornation.
As was discussed earlier, the likelihood that an impostor
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could have possession of the auto-dialer 100, know all
three of the keywords and their associated PINs, and have
a voice quality, retina shape, fingerprint or facial
construction reasonably similar to that which is
indicated from the data held in the auto-dialer 100, is
not great. Because of the availability of other methods
of preventing the use of recordings as a substitute for
an authorized voice, and similar techniques known to
prevent duplication of other biometric features, it is
reasonable to reduce the level of file detail which is
used when the auto-dialer 100 is used to control access
to a facility.
Alternatively, in some cases, it may be
appropriate to use the data of the auto-dialer 100, or an
aspect thereof, to provide the basis for a system look-
up of biometric or voice data related to the presumed
user of the system. In this manner, the data which is
transmitted from the auto-dialer 100 may include an alpha
and/or numeric string of data which the interfacing
equipment will use as the basis of accessing a record or
group of records which contain voice or other biometric
details of the user. In this manner, the requirement for
manual input of identification to initiate the access of
the relevant records is eliminated and results in a
faster, less error-prone access system to such records.
In yet another embodiment of the present
invention, the RAM 108 is programmed to store information
needed to generate a visual representation of the
authorized user of the device. In response to a command
to output such data, e.g., the activation of one or more
control keys by the user or the receipt of a particular
stored set of DTMF tones representing a command to output
the data, the auto-dialer 100 will generate a series of,
e.g., encoded DTMF tones which represent stored data
needed to generate the visual representation of the
authorized user. A device receiving such information may
decode the image information and generate a visual
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representation of the authorized user. Because the auto-
dialer 100 can transmit such data over standard telephone
lines, the ultimate device receiving and displaying the
. representation of the user may be located at a location
which is remote to the auto-dialer 100. This feature may
be used as part of a security system wherein it is
important to obtain data that can be used to visually
confirm a person's identity or in conjunction with an
emergency, e.g., a 911 system, such that the receiving
station would be able to receive an a physical
representation of the user/caller, thus enabling the
location of such person in distress. This feature may be
particularly significant with auto-dialers designed for
use by smaller children who, if in distress could quickly
transmit a physical representation, rather than
attempting to rely on the youngster to provide
information (e. g. hair color, height weight, etc.).
For computer database access, the use of voice
recognition in conjunction with the system described
above, a conventional telephone or, more simply, a small
microphone with interfacing circuitry, would be connected
to -the alternate RJ11 port~of the enhanced modem.
Following the connection to the enhanced switching system
by the method described earlier, and the transmission
from the enhanced modem, based upon its earlier receipt
of a processed voice file which the user provided in the
initialization procedure, to the switching system, with
its ability to provide voice recognition, the RJ11 port
into which the requesting user's telephone or microphone
is connected, would be electrified, and, at which time
the user would be provided with a voice or screen prompt
indicating that the user should pronounce one or more of
those voice samples which the switching system could
evaluate. Upon satisfaction that the currently provided
voice sample reasonably matches that which had been
recorded earlier, the process of querying the target
database can continue, and if appropriate, connection
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among the requesting user and the target database is
completed. By the central provision of voice processing
as a method of screening access users, substantial
economic advantages are provided to each of the target
databases, each of whom would save the cost of such an
installation and requisite set-up costs for each user,
etc.
F. PIN Scheme
While the auto-dialer 100 of the present
invention can be programmed to work with a variety of
known personal identification number (PIN) schemes, both
as a method of controlling access to data within the
autodialer 100, as well as a method to provide access to
security interfacing devices, it may also be used with
the new and novel PIN scheme of the present invention.
In accordance with the PIN scheme of the
present invention, a user is required to select a
plurality of different PINs with each PIN being
associated with a keyword or phrase that the user may
also select. The keyword or phrase is intended to help
remind the user of the PIN. For example, a user may
select his social security number as a PIN that is to be
associated with the phrase "social security" or a user
may select the street number of his residence as a PIN to
be associated with the keyword "house".
Once a user selects a plurality of such PIN
numbers and associated phrases, the PIN numbers and
phrases are stored in the autodialer's memory at, for
example, the time the device is initialized by being
programmed with user specific data.
In this manner, as with the voice recognition
security scheme described above, the auto-dialer 100 is
used to store important identification information, i.e.,
the key words and phrases and PIN numbers associated
therewith, alleviating the need for storage of this
information at the service facility or device which is
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being contacted by the auto-dialer 100.
In accordance with the PIN scheme of the
present invention, when placing a call to a destination
number not on a preprogrammed speed dial list stored in
the RAM 108, or initiating another transaction, the auto-
-_ dialer 100 transmits to the service receiving the call,
the stored list of key words and phrases and the PIN
numbers associated with the key words and phrases. The
transmission of this information is done in an encrypted
form, e.g., by using the DTMF data encoding scheme of the
present invention, to prevent an unauthorized user from
learning the PIN number information.
After receiving the list of key words and
phrases, and PIN numbers associated therewith, the
service receiving the call selects one of the key words
or phrases and prompts, e.g., by a voice request, the
auto-dialer user to supply the PIN number associated with
the selected key word or phrase. The user may supply the
requested PIN number by using, e.g., the keypad of the
telephone which is being used to make the call.
Alternatively, if the se price facility is capable of
receiving and interpreting voice data, the user may
provide a voice response to the offered key word.
In accordance with the present invention, if
the user provides the correct PIN number in response to
the prompt, the desired action, e.g. placement of a call,
is perf orined .
However, if the wrong PIN number is provided,
the user is given a second prompt to enter the requested
PIN again and to enter a second PIN associated with a
second key word or phrase selected from those supplied by
the auto-dialer 100. Only upon entry of the correct
first and second requested PINS is the user given access
to the requested service.
If the user fails to enter correct PINS in
response to the second request, the user is given another
prompt requesting that the user enter the first two PINS
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that were requested as well as the PIN associated with a
third key word or phrase selected from the list supplied
by the auto-dialer 100.
If the user enters all three requested PIN
numbers in response to the third prompt the user is given
access to the requested service, e.g., the desired call
or transaction is completed.
However, in the event that the user fails to
provide three correct PINs in response to the third
prompt, the user is given no more chances to enter PINs.
In response to the third failed attempt to
enter the requested PINs, the user is instructed to place
the auto-dialer 100 in close proximity to the speaker of
the telephone. An acoustic signal is then sent to the
auto-dialer 100 instructing it to deactivate itself. In
addition, the records of the central office are updated
to indicate that the auto-dialer 100, which was used to
place the unsuccessful call, is not longer an authorized
device. This prevents the particular auto-dialer 100,
which was being used by an apparently unauthorized, from
being used again in the future to place calls unless it
is reactivated by, e.g., the central office.
Additionally, or alternatively, the service provider may
mark its records to disallow any further requests from
the particular auto-dialer 100.
After the tone to deactivate the auto-dialer
100 is transmitted, the user attempting to place the call
with the auto-dialer 100, is instructed to call a central
service office to have the auto-dialer 100 reactivated.
Upon contacting the central service office
further steps can be taken to determine if the auto-
dialer 100 was stolen or if the user merely had
difficulty entering the correct PINS for some other
reason. Since the auto-dialer 100 can be reactivated
via, e.g., an acoustic command signal which can be
received from a standard telephone, the auto-dialer 100
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can be readily reactivated by the central service office
when the authorized user calls requesting such re-
activation.
In another embodiment, the key words or phrases
and associated PIN information is not transmitted to the
-. switching service receiving the call. Instead, when a
user attempts to use a function which is protected by
this security method, the auto-dialer 100 uses its pseudo
random number generator to select a keyword or phrase
from the list of words and phrases stored in the auto-
dialer's memory. The user is then prompted by, e.g.,
displaying the selected key word and phrase on the device
202. The auto-dialer 100 then selects a set of numeric
sequences to serve as a list of possible PIN numbers.
The list of possible PIN numbers associated with the key
word or phrase is then displayed with the correct PIN
with the list serving as camouflage for the valid PIN.
The user is then required to scroll to the
correct PIN number from the list of PINs, by, e.g., using
the keys of the input device 105, before the user will be
permitted to place a call or access a protected function.
To facilitate this process; in one embodiment, the
placement of the correct PIN can be 'locked' into place,
such that the user, when seeing a particular key-word,
will, by memory, know that the correct PIN is situated in
a particular place, e.g., two button presses of the left
key.
In the event that an incorrect PIN is selected
as a response, the user is prompted a second and a third
time, if necessary, as previously described above.- In
the event that the user fails to respond with all the
requested PINS in response to the third prompt, the auto-
dialer 100 will deactivate itself and give the user a
message to contact a service center as previously
described.
While the above described PIN security method
of the present invention requires a user to remember more
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then a single PIN number, the keyword or phase memory
association feature makes it easy for an authorized user
to remember the required PIN numbers.
While it might at first appear that the above
PIN security method makes it easier for an unauthorized
user to guess the correct PIN number, it should be noted
that because multiple PIN numbers are used and there is
no fixed pattern in which they will be requested, it is
unlikely that an unauthorized user will be able to
repeatedly guess the correct PIN numbers.
Furthermore, the fact that the auto-dialer 100
is designed to inactivate itself in response to multiple
failed attempts to select a correct PIN number in
response to a prompt or in response to a signal from the
central office, until being reactivated by, e.g., entry
of a re-activation code in the form of a pre-selected
sequence of DTMF signals, greatly decreases the chances
of an unauthorized user being able to use the auto-dialer
100 to make multiple calls even after guessing one or two
PIN numbers.
The incorporation of on-device security, such
as the above-described embodiment, does not preclude the
use of the same techniques when the auto-dialer 100 is in
communications with a switching office. In fact, the
present invention anticipates that in some cases the same
method will be used in different situations. For
example, in one embodiment when the auto-dialer 100 is
directed to initiate a call to switching office, the data
relating to user's selections of keywords and associated
PINs is also transmitted using the indexed tone system.
If the switching service requires further identity
verification prior to the placement of the call, it will
select one of the keywords and its associated PINS and
provide a voice prompt for the user to enter, or speak,
the correct PIN.
By the use of a common method of securing the
use of the auto-dialer 100 for preprogrammed uses, both
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on-device and through voice prompts when connected to a
switching office, ease of use is enhanced without
diminishing the security needed to protect the
information contained within the auto-dialer 100.
Additionally, it permits the use of the auto-dialer 100
for secured transaction with off-line system which may
not have the ability to provide voice prompts, e.g.
current debit/credit card input devices.
G. Use of Input Keys to Enable Auto-dialer
Operation
While the use of PIN numbers and PIN security
methods add a degree of security to various transactions
involving the use of the auto-dialer 100, in one
embodiment the pressing of a sequence of buttons is used
as a password to enable the operation of one or more
features associated with the particular password or
sequence of buttons. In such an embodiment, a sequence
of buttons which are, e.g., part of the input device and
selected by, e.g., the user, to be associated with all
such secure functions of the auto-dialer 100 are stored
in the R.AM 108. Before a function associated with the
password is enabled, the auto-dialer 100 requires a user
to activate the stored sequence of buttons. If the
stored sequence of buttons is entered, the auto-dialer
100 enables the associated function. However, if a user
attempts to enable a function by pressing buttons in a
sequence other than the selected stored sequence, and
does this for more than X times, wherein X is a pre-
selected integer, e.g., 3, the processor 104 will disable
the auto-dialer 100 until the device receives acoustic
instructions, e.g., acoustic signals to enable the auto-
dialer 100, from e.g., a central office responsible for
maintaining records on the auto-dialers 100.
Significantly, in this embodiment, the user is enabled to
establish which aspects of the device function must be
preceded by the entry of a particular password or
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sequence of buttons.
H. Additional Security Features
In addition to the PIN and other security
schemes described above designed to reduce the number of
unauthorized calls that are permitted to be completed, in
accordance with one embodiment of the present invention,
yet another screening technique is used.
In accordance with this embodiment of the
present invention, a telephone switching office is
designed to receive calls, e.g., placed with the auto-
dialer 100, which are intended to be connected to the
destination telephone numbers indicated by the caller.
These destination telephone numbers may represent various
service providers, e.g., telephone long distance
carriers, computer networks, credit card companies, etc.
As discussed above, one problem is that such
service providers, which may have a relatively limited
number of telephone ports, are frequently overwhelmed by
the number of calls generated by hackers trying to gain
unauthorized access to the service provider.
In accordance with the present invention calls
to multiple service providers must first pass through the
central telephone switching office used to process calls
from auto-dialers 100. The central telephone switching
center, with its relatively large number of phone ports,
provides a convenient point of intercepting many of the
calls from hackers preventing them from jamming the
smaller number of phone ports which may service providers
have.
In accordance with the present invention, in
one embodiment, this intercepting or screening function
is provided by sorting calls to particular service
providers, arranging identification information or other
caller information into an orderly format suitable for
using in a data base search.
After arranging the identification information
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or other caller information into the desired format, the
central switching office contacts the service provide
via, e.g., a dedicated high speed link, providing the
' information on the caller and requesting the service
provider to indicate whether or not it wishes to service
the call.
In response to the query by the central
telephone switching office the service provider checks a
database of authorized clientele to determine if the
information provided by the central office indicates that
an authorized user is calling or a hacker is calling.
If, after a quick search of its database, it appears that
an authorized user is attempting to call the service
provider, the service provider indicates to the central
telephone switching office that it will accept the call
and the call is connected to one of the service
provider's local telephone ports.
On the other hand, if the service provider
indicates that it believes the caller to be a hacker, and
therefore indicates it does not want to accept the call,
the call is not connected to the service providers local
telephone port. Instead, ehe central telephone switching
office traces the call and/or takes other action
appropriate for dealing with the caller who is believed
to be a hacker.
While the above scheme requires a communication
link or telephone connection between the central
telephone switching office and the service provider it
does not require the service provider to support the
number of telephone ports that would otherwise be
required to deal with telephone calls from hackers.
Accordingly the above described method of
filtering or intercepting calls before they reach the
local telephone ports of telephone service providers
offers potential cost advantages by reducing the amount
of telephone equipment the service provider must
purchase.
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II. Use of Non-Standard Signals
In yet another embodiment of the present
invention, after the auto-dialer 100 connects to, e.g., ,
the local telephone switching office which, in response
to the signals of the auto-dialer 100, creates the first
connection, to a service provider, e.g., a long distance
carrier designed to operate with the auto-dialer 100, the
auto-dialer 100 stops transmitting data using standard,
un-encoded DTMF signals and by the use of switches to
another data format to transmit data, such as billing
information, e.g., encoded DTMF signals or signals of a
frequency other than standard DTMF, to the service
provider. For example, the auto-dialer 100 may begin
placing a call by outputting the necessary DTMF signals
required to connect to a selected long distance carrier.
Once connected to the selected long distance carrier,
assuming that at the time that the auto-dialer 100 was
programmed, the long distance carrier was known to be
capable of decoding encoded DTMF signals and/or signals
of non-DTMF frequencies, the auto-dialer 100 transmits
billing data in the form of tone pairs comprising tones
having a multiple of the normal number of frequencies
used for standard DTMF tones. Such signals which are
non-standard DTMF signals, may be generated with relative
ease using the same basic circuitry used to generate
standard DTMF tones. However, because of the tones non-
standard frequency, they will not be recognizable to
standard telephone switching circuitry making the data
represented by the non-standard DTMF tones more difficult
to interpret and use in later unauthorized transactions.
There are numerous advantages in using non-standard
frequencies. First, they are not easily created using
conventional phone equipment or modems, thus creating a
reduction in the likelihood of fraud. Second, is the
much greater data transmission speed that can be achieved
using more than two simultaneously transmitted
frequencies. In fact, four frequencies, can transmit
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data at many times the rate which can be achieved with
two frequencies, assuming that the frequency ranges can
vary throughout the full voice band (avoiding those
' frequencies which are already reserved for in-band
signaling). As a result of the increased speed, less
-- time is required to transmit data, thus reducing the cost
of the call.
III. Convenience Features
It should be noted that while the numerous
above described features of the auto-dialer 100 are
directed primarily to security concerns, many of the
features make the auto-dialer 100 easier to use than the
manual alternatives.
Referring now to Figs. 10A, lOB, lOC, lOD and
l0E which show various views of an auto-dialer 100
implemented in accordance with one exemplary embodiment
of the present invention, some of the convenience
features resulting from the general shape of the auto-
dialer housing 101 will be described.
Referring not to Fig. l0A their is illustrated
a bottom planar view of the auto-dialer housing 101. As
illustrated the housing comprises the head portion 103
which has a generally circular appearance when viewed
from above or below, an elongated handle section 104,
audio output ports or openings 105 and a depression or
indentation 141 used for centering the auto-dialer 100
with a matching housing of e.g., an automatic teller
machine. In addition, the housing includes a light
reflective surface 106. The auto-dialer housing 101 also
includes a ring collar 107 which can be attached to,
. e.g., a key ring for convenient storage.
As described above, the generally small size of
the head portion 103 facilitates alignment of the auto-
dialer 100 with the center of the microphone of a handset
121 while the notch 141 aids in inserting the auto-dialer
100 with a corresponding housing on a receiver of a
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device which is designed to receive data from the auto-
dialer 100.
Referring now briefly to Fig. lOB there is
illustrated a top view of the auto-dialer housing 101.
From this view, the switch 131 which can be depressed to
activate the auto-dialer 100 or to select an item
highlighted in the display screen 202 can be seen.
Scroll buttons 119 which can be used to cause the screen
display to scroll is also illustrated. To facilitate
easy one handed operation of the switch 131 and/or scroll
buttons 119 using the same hand used to hold the
autodialer 100, the scroll buttons 119 and switch 131 are
located on the top side of the housing 101 within 6
centimeters of the end of the housing's elongated handle.
The display device 202 is visible from the top
thereby permitting a user to see messages and other
indications of activity while the auto-dialer 100 is
positioned in close proximity to the speaker or
microphone of the telephone handset.
Referring now to Fig. lOC a side view of the
auto-dialer housing 101 is illustrated. From this view,
the generally slender shape of the auto-dialer 100 can be
seen. As illustrated, in one exemplary embodiment, the
auto-dialer 100 is approximately 7 cm long and 1.65 cm
wide. This small size and slender shape make the auto-
dialer 100 easy to hold in a single hand and to transport
and store in a pocket of a users shirt or pants.
Referring now to Fig. lOD, a cut away side view
of the auto-dialer 100 is shown. The general internal
arrangement of the elements which comprise the auto-
dialer 100 are visible from this view. In the
illustrated embodiment, a circuit board 117 is used to
mount the microprocessor 104 and other circuitry
previously described. A liquid crystal display 202 is
mounted above the circuit board 117 and below a clear
plastic window 201 located in the top of the of the
housing 101.
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The speaker 114 is positioned over the openings
105 and in electrical contact with the circuit board 117.
The battery 208 is located between the circuit board 117
' and the speaker 114 as illustrated.
To protect the contents of the housing from
_- water and dirt, a water resistant membrane 109 is
positioned between the speaker 114 and the openings 105
to prevent water from entering the inside of the housing
101 while permitting sound to exist the housing 101
through the openings 105. In addition, rubber gaskets
and control buttons 133 are used to prevent entry of dirt
and water from the top side of the auto-dialer housing
101.
To provide a convenient way of storing the
auto-dialer 100 on, e.g., a key chain, the housing 101
includes a rotating ring collar 107.
One significant convenience feature of the
present invention has to do with its physical shape which
permits it to be stored on a key chain such as the key
chain 125 illustrated in Fig. 10E. As illustrated in
Fig. 10E, the auto-dialer case 101 includes ring collar
107 in the elongated portion 104 of the housing 101 which
extends from the generally saucer shaped head portion
103.
Studies have shown that most people are far
less apt to forget to take their keys with them when they
go out shopping, to the office, etc., than they are to
forget their wallets or a specific card usually contained
in the wallet. Furthermore, when they do forget their
keys, they are frequently reminded to return to the place
where they left them as soon as they are unable to open
their car, house, or office door because they left there
keys behind. Comparatively, people often leave
credit/debit cards behind following their use, and tend
to take much longer to recall the absence of the card
than key rings that are left behind.
The auto-dialer 100 of the present invention
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takes advantage of this relatively unique aspect
associated with key rings by being designed to be mounted
on a key ring 125. In this manner, the auto-dialer 100
is designed to be as readily accessible as standard keys
127 on a key ring and to move from place to place with
the authorized user the same as an ordinary physical key
127.
The small size of the auto-dialer 100 and
relatively smooth yet durable surface which may be made
of plastic or other suitable material also facilitates
the transportation and storage of the device. For
example, the device may be stored in a persons pocket and
transported from place to place as the user moves
throughout the day in the same manner as a standard
mechanical key can be moved about.
The generally water resistant construction of
the housing 101 provides yet another convenience feature
in that a person need not be concerned about taking the
device to wet or damp locations which might prove
damaging to other electrical devices.
Accordingly, it is apparent that the size,
shape and durable nature of the housing 101 used to house
the auto-dialer 100 all provide the convenience of
portability and low maintenance.
The relatively limited number of buttons 131,
119 used to operate the auto-dialer 100, e.g., less than
5 buttons, provides yet another convenience advantage,
i.e., control simplicity. Furthermore, because of the
auto-dialer's shape and positioning of- the control
buttons 131, 119 it is relatively easy to operate the
auto-dialer 100 using a single hand by scrolling to
desired options displayed in the display 202 and
selecting the option or telephone number selected by
pressing the button 131.
Accordingly, the auto-dialer's design
illustrated in Figs. l0A-l0E provides a device that
facilitates use by handicapped individuals who may find
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it difficult to operate devices with more keys or
requiring two hands to use.
Other convenience features result not from the
' shape of the auto-dialer's case 101 but from its ability
to provide data compression features. For example,
--_ because the auto-dialer 100 is capable of encrypting or
encoding calling card number information directly into a
telephone number, the time required to place a call using
a calling card number can be substantially reduced.
Furthermore, the user need not remember the calling card
number since it is programmed into the auto-dialer 100.
In addition, since a user need not manually input
telephone number and calling card number information, the
chance of having to repeat a dialing sequence because of
an input error is greatly reduced.
Furthermore, because the auto-dialer 100 can be
programmed using acoustic signals programming of the
auto-dialer 100 can be performed via a standard telephone
connection with a remote service center. Thus, a user
need not program the auto-dialer 100 but merely has to
call the remote service center and place the auto-dialer
100 in close proximity to the speaker of the telephone.
The remote service center can than program the auto-
dialer 100, by sending the auto-dialer a series of
acoustic signals, in accordance with a user's request.
In addition to the convenience features already
described, the auto-dialer 100 can be programmed to place
international calls and to insert pauses, where required
in a dialing sequence, to permit for proper telephone
connections. The memory of the auto-dialer 100 can also
be used to store international calling codes, area code,
and other types of dialing information making it
' relatively easy for a user to place long distance calls
from foreign countries.
While the security and other features of the
present invention have been generally described above in
regard town auto-dialer embodiment. It is to be
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understood that the above described features can be
incorporated into a wide variety of devices where
security is of concern.
For example, the above described technique of
encrypting data into standard DTMF signals and other
signals comprising a series of tones may be used in a
host of telephone, security and other communications
applications. For example, features of the present
invention may be included in telephones which are coupled
electrically, as opposed to acoustically, to telephone
lines.
In addition, the security features of the
present invention may be incorporated into standard lock
devices, computer network security devices and other
systems where it may be useful to use a series of
acoustic or electrical signals as an access key.
In one embodiment of the present invention some
of the features described above are incorporated into a
facsimile machine to provide a degree of security to
insure that only the party or individual intended to
receive a facsimile is in fact the party that receives
the message.
In its most general form, the facsimile
embodiment of the present invention includes a facsimile
machine which transmits an identification code, e.g., the
recipient's name, or the device number of the user's
device, to a receiving facsimile machine. The code is
used to identify the person or party to which the
facsimile is directed. The transmitting facsimile
machine may also transmit a specific PIN or other code
which the receiving machine will require to be entered
before the facsimile is printed out. In accordance with
this facsimile embodiment, the facsimile machine
receiving a facsimile message will store the message in
electronic form, e.g., in memory or on a hard disk until
it receives the proper PIN or code which matches the PIN
or code transmitted with the message.
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In this manner, only the person to which the
facsimile message is directed, e.g., a person who knows
the transmitted PIN or code will be able to print and
read the transmitted message.
In accordance with the present invention the
information identifying the person to whom the message is
directed, the PIN, and/or other code transmitted to the
receiving facsimile machine may be transmitted using the
data encoding scheme, e.g., DTMF data encoding scheme,
described above.
In addition, to provide a heightened degree of
security, the PIN or code that must be entered into the
receiving facsimile machine may also be an encoded DTMF
signal which may be programmed into the auto -dialer 100
of the individual to whom the message is directed. To
obtain a printout of the facsimile message, the user of
the auto-dialer 100 can supply the PIN or code number
required by the facsimile machine either acoustically or
electrically using the auto-dialer 100 to generate the
required encoded DTMF signal which would be programmed
into the auto-dialer's memory.
In this manner, the auto-dialer 100 can be used
as a key to enable the printout of facsimile messages
from a secure facsimile machine in accordance with the
described embodiment of the present invention.
Even where data security concerns are not
significant, the data compression and other convenience
features of the present invention make the present
invention's various features suitable for incorporation
into a number of consumer device, e.g., fax machines,
computers, etc.
To facilitate the use of the auto-dialer 100 as
' a debit/credit card, e.g., in toll transactions, a
secondary input/output device with a higher data rate
than that of the acoustic coupling device may be
incorporated into the auto-dialer 100. In one
embodiment, an infrared transmitter/receiver device is
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incorporated into the auto-dialer 100 to provide for the
rapid exchange of debit/credit information at toll booths
and turnstiles. In accordance with this embodiment, a
corresponding infrared receiver/transmitter device
located at the toll booth or turnstile is used to
interact with the auto-dialer 100 and to credit or debit
money to an account maintained for the purposes of toll
payment.
In another embodiment the auto-dialer 100
includes a secondary input device for acquiring user-
related data, as opposed to data which otherwise would be
stored in the ROM 106. In such an embodiment, the
secondary input device may be coupled to a mated
transmitter where the method of transmission is, e.g.,
modulated light signals, radio signals, or electrical
signals transmitted to the device by a direct electrical
coupling. For example, the connection of a modular jack
of a handset to a compatible interface which is part of
the auto-dialer 100 may be used as such a secondary data
input.
In another embodiment, the auto-dialer 100,
using either the acoustic communications method described
above, or one or more of the secondary communications
methods can be used as a portable automatic
identification device. For example, upon receiving a
package from a courier, a user could place the auto-
dialer 100 within a proximate distance of the courier's
data input equipment to record the users name and other
information. As the emitted request from the courier's
data-input device would use the data encrypted, method
described above. In an embodiment where the data was
encrypted or encoded using the auto-dialer's system
clock, the received data would be system-clock dependent,
thus substantially avoiding the risk of forgery
associated with current signature based identification
systems. If further certainty was required as to the
receiving person's identity, as might be the case with
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valuable papers, the requesting interface equipment could
send a request to the user's auto-dialer 100 which would
require that the user to unlock the auto-dialer 100 using
' any one of the many methods described earlier. Through
the use of the auto-dialer 100 as a portable, digital
--, identification device, the current practice of storing
paper to preserve a person's signature could be
eliminated.
The advantage of using the auto-dialer 100 as a
portable identification device is also useful in
controlling access to electronic documents among
computers when it is advantageous to have, at the
receiving end, some degree of certainty as to user's
identity, and, when appropriate, the ability to have a
higher level of certainty which can be accomplished
through the use of voice verification or other security
features as discussed above.
The use of the auto-dialer 100 to facilitate
transactions in a secure manner has been discussed at
length above. The practical convenience of the auto-
dialer 100 as both an on-line and off-line transaction
device enables substantial advantages to both the user
and the counter-party. In an on-line environment, where
substantial data regarding the user is available, the
processing of the transaction is enabled by the auto-
dialer's ability to quickly and securely transmit that
information which is needed for the interfacing equipment
to locate the relevant records, and make those
computations and database searches which relate to the
transaction. Since the auto-dialer 100 communicates on a
non-contact basis using, e.g., sound, light, etc., the
interfacing equipment to transmit such data is less
' expansive, more reliable, and easier to maintain than
that which is needed with magnetically cards which stores
information on magnetic strips with their inherent
limitation for data storage.
It is widely known that the cost of on-line
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transactions, e.g., interactive computer transactions is
expensive. In many transactions, on-line or real time
processing of data or requests is unnecessary. However, ,
on-line transactions make it possible to use a
centralized data base with a higher degree of security
than can be associated with de-centralized processing of
information, e.g., credit and debit information. Since
the auto-dialer 100 provides substantial protection
against both fraudulent use and tampering, the auto-
dialer 100 can be used for secure transactions and
debit/credit processing without the need for a
centralized secure data base which might otherwise be
required to achieve the same level of security. Further,
its use as a transaction instrument for over the phone
transactions, without the need for any local interfacing
equipment, other than a telephone, enables far more
transactions to be handled in this manner, thus improving
convenience for activities such as voting, bill payment,
and other transactions currently requiring written
signatures, personal appearance, or other means of
identification not presently communicable, with
certainty, over the phone or via facsimile machine.
The use of the auto-dialer 100 in on-line
transactions, when compared with the common method of
using magnetically-striped plastic cards, with their
vulnerability to be easily copied and read, their
inherent ability to store substantial data, the physical
vulnerability of the card to scratches, etc., is more
convenient because one auto-dialer 100 can accommodate
substantial, multiple purposes and data and because the
auto-dialer 100 has inherent security features as
discussed above.
IV. Additional Embodiments and Features
In addition to the above described embodiments,
the auto-dialer 100 can be implemerred as a pager or
beeper device. Alternatively, only particular selected
features of the auto-dialer 100 may be incorporated into
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a pager device. For example in one such embodiment, the
display of the device comprises a screen suitable for
displaying text messages. In such an embodiment, the
processor 104 decodes and displays messages and other
data that is received, e.g., in the form of encrypted
DTMF tones. In the more standard auto-dialer embodiment,
a screen may also be included for the display of
information and data.
As part of the central or local office computer
system according to the present invention, a central
office computer has the ability to receive, decode and
process encrypted DTMF signals, the computer system may
also include the necessary data transmission circuitry
required to relay information received in encrypted DTMF
signal form to a paging device. Such transmission may
include the steps of decoding the data and then re-
transmitting the data with the data being preceded by
paging device address information.
While the above description of the present
invention was discussed largely in terms of an auto-
dialer embodiment, it will be apparent to those skilled
in t-he art that the features of the present invention are
not limited thereto but may be embodied in a wide variety
of communication and other security devices.
Accordingly, nothing in the above description is intended
to limit the scope of the present invention to the auto-
dialer embodiment described above. Furthermore, any
reference to any specific set of tones, except as they
may relate to those tones needed to establish the first
link of a call, i.e. DTMF, should not be interpreted as
the only frequencies or tone patterns which the features
of the present invention are appropriate and useful.
It should be noted that the above headings
provided in the detailed description of the patent
application are merely provided as an aid to the reader
of the detailed descriptions. It is intended that the
various sections of the detailed description be read
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PCT/U S95109964
together and viewed as a whole for what they teach and
describe of the present invention.
