Note: Descriptions are shown in the official language in which they were submitted.
2007537
METHOD AND APPARATUS FOR CONTROLLING
A TEL~nOh~ ANSWERING DEVICE
Field of the Invention
5The present invention relates generally to
telephone answering devices. In particular, the present
invention relates to a control circuit for a telephone
answering device.
Background of the Invention
It has been customary, to date, to consider a
telephone answering device as basically a tape recorder
attached to a telephone. In general, recording of outgoing
messages (OGM) on a telephone answering device (TAD) has been
done through a microphone installed in the base of the TAD.
One problem with this is that it can be difficult to get
close enough to the microphone in order to input a message,
especially if the TAD is in a wall mounted position.
Furthermore, due to the omnidirectional nature of such a
microphone, and the greater distance of the user from the
microphone, a great deal of background noise is recorded
making it difficult for a listener to understand a recorded
message. Another problem that arises is the amount of tape
noise recorded due to the proximity of the tape drive to the
microphone.
A further problem with prior art TADs has been
that only the telephone attached to the TAD will cause the
TAD to stop playing or recording a message once the handset
of the telephone has been picked up. A person who picks up
an extension telephone in another room is incapable of
disabling the TAD and consequently must wait for the TAD to
complete its processes before starting a conversation with
the caller.
Summary of the Invention
The present invention integrates the TAD with the
telephone, thus allowing messages to be recorded directly
through the handset microphone of the telephone. By doing so
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tape noise is eliminated. Furthermore, as the user is closer
to the mouthpiece of the handset a greater sound pressure is
realized at the microphone thus improving the signal-to-noise
ratio significantly, thereby greatly reducing any background
noise recorded. Moreover, with the present invention a user
feels more comfortable and less intimidated while recording
messages.
The present invention also allows a user to pick
up any telephone connected to the same line as the telephone
answering device, and in doing so disable the functions of
the TAD, thus providing remote control of the TAD.
Stated in other terms, the present invention is a
control circuit for a telephone answering device, the
control circuit controlling electrical connections between
the telephone answering device, a telephone line, and a
telephone set electrically connected to the telephone line,
wherein the telephone set is provided for conducting
telephone conversations on the telephone line and for
recording messages on the telephone answering device, the
control circuit comprising:
auxiliary power means for powering the telephone
set when the telephone set is electrically disconnected from
the telephone line;
first switch means for selectively disconnecting
the telephone line from the telephone set, and circuitry
within the control circuit, and connecting the telephone set
to the auxiliary power means; and
second switch means for actuating the first switch
means;
said first and second switch means responsive to a
control signal from the telephone answering device, the
control signal actuating the second switch means which
thereby actuates the first switch means to disconnect the
telephone line from the telephone set, and the circuitry
within the control circuit, and to connect the auxiliary
power means to the telephone set, whereby speech signals from
the telephone set are provided to the telephone answering
device for recording.
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Stated in yet other terms, the invention is a
control circuit for a telephone answering device which is
electrically connected to a telephone line having at least
one telephone set electrically connected thereto, the
telephone line providing power for the telephone set, the
control circuit comprising:
first and second storage means for storing an
electrical charge resulting from the power appearing on the
telephone line;
first and second discharge means for discharging
the first and second storage means, respectively, at
different rates to create a transitory voltage differential
between the first and second storage means, the transitory
voltage differential occurring whenever the at least one
telephone set goes to an off-hook state, thereby producing a
voltage drop on the telephone line; and,
control means, activated by the voltage
differential between the first and second storage means, for
cancelling operations of the telephone answering device and
placing the telephone answering device in an on-hook mode.
Stated in still other terms, the invention is a
method of disabling a telephone answering device, the method
comprising the steps of:
detecting the transition of a telephone set from
an on-hook state to an off-hook state, the telephone set
being connected to a telephone line to which the telephone
answering device is also connected; and,
generating a signal in response to the detection
of the transition which thereby cancels any operations of the
telephone answering device and places the telephone answering
device in an on-hook mode.
Stated again in other terms, the invention is a
method of controlling a telephone answering device, the
method comprising the steps of:
selectively disconnecting a telephone set,
electrically connected through the telephone answering device
to a telephone line, from the telephone line;
Z007537
powering the telephone set when the telephone set
is disconnected from the telephone line;
connecting a microphone contained in a handset of
the telephone set, to recording circuitry within the
telephone answering device when the telephone set is
disconnected from the telephone line, thereby allowing speech
information impinging on the microphone to be recorded by the
telephone answering device;
detecting the transition of at least one other
telephone set, connected to the telephone line, from an on-
hook state to an off-hook state; and,
generating a signal in response to the detection
of the transition which thereby cancels any operations of the
telephone answering device and places the telephone answering
device in an on-hook mode.
Brief Description of the Drawings
The invention will be readily understood by the
following description of a preferred embodiment, by way of
example, in conjunction with the accompanying schematic
drawing of a control circuit according to the present
invention.
Detailed Description of the Invention
The attached figure illustrates a control circuit
10 within a telephone answering device (TAD) 20 which is
capable of both providing access to a microphone MKl in a
telephone handset 40 (connected to the TAD 20) for recording
of messages on the TAD 20, and for disabling the functions of
the TAD 20 when any telephone, connected to the same
telephone line 60 as the TAD 20, is taken off-hook.
When it is desired to record an outgoing message
(OGM), the telephone answering device 20 is placed in a
recording mode so as to record any signals onto a resident
storage device (not shown) via the record circuitry 50. In
activating the recording mode, a central processing unit
(CPU) 70, internal to the TAD 20, forces lead V to go to a
state of high potential, thus causing transistor Q3 to turn
;~00753~
on (via resistor R4). This in turn powers relay coil Ll,
thereby actuating its contacts Kl to disconnect from the
diode bridge (Dl, D2, D3, D4) consequently isolating the
telephone line signals appearing on the leads TIP and RING
from the telephone handset 40. The disconnection of the
telephone handset 40 from the diode bridge (Dl, D2, D3, D4)
further leads to power from the telephone line 60 (generated
at the telephone company's central office) to be disconnected
from the telephone handset 40, and thus no power is supplied
to a telephone transmission circuit 30 in the telephone
handset 40. However, when the relay Kl is switched from the
diode bridge (Dl, D2, D3, D4) it connects a current path
which flows from Vcc through the resistors R2 and R3 and
through the contacts of the relay Kl to the telephone
transmission circuit 30. With auxiliary voltage thus applied
the telephone transmission circuit 30 resumes functioning,
allowing the microphone MKl to be used to transmit signals to
the TAD 20 for recording.
The signal to be recorded must pass through
transistor Ql which is controlled via power supplied to the
base of transistor Ql from transistor Q4. Transistor Q4 is
controlled by either a signal appearing on lead V, via
resistor R5 and diode D6, or by a signal appearing on lead W,
and is biased by resistor R7. If either of lead V or lead W
is in a state of high potential, Q4 will be turned on, thus
supplying power to the base of transistor Ql. The signal
appearing on lead W is generated by the CPU 70 and is
representative of the TAD 20 going to an on-line state to
record incoming messages on the telephone line 60. Resistors
R6 and R8 provide biasing for transistor Ql.
All incoming signals to be recorded pass through
the inductor L2 ~o the transistor Q2. Transistor Q2 is
controlled via transistor Q5 which in turn is controlled by a
signal X generated by the CPU 70. Resistors R9, Rll, and R12
provide biasing for the transistors Q2 and Q5. The signal X
is used to indicate when recording is in operation. Thus
when signal X is of high potential, transistor Q5 conducts
and consequently places transistor Q2 in a state of
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_ 6
conduction.
After the recording has been completed, the TAD 20
is taken out of its record mode. Consequently the CPU 70
forces lead V to a low potential, thus causing contacts Kl to
reconnect back to TIP and RING. The auxiliary power is
disconnected at the same time, and power to the telephone
handset 40 is once again obtained from the telephone line 60.
At this point, any incoming signals from the telephone line
60 will be monitored by the TAD 20.
In normal operation, if the TAD 20 is in a mode to
monitor the telephone line 60, any calls received will be
processed by the TAD 20. The TAD 20 monitors the telephone
line 60 through the monitor and playback circuitry 80
internal to the TAD 20. During monitoring of the telephone
line 60, an indication of any ringer signals detected by the
circuitry 80 is provided to the CPU 70. Upon reception of a
ringer signal, the CPU 70 instructs the circuitry 80 to
answer the incoming telephone call by setting the telephone
line 60 in an off-hook state. This is performed by the
circuitry 80 which places a resistive load therein (not
shown) on the telephone line 60, thus causing the voltage on
the telephone line 60 (supplied from the telephone company's
central office at a level of approximately 48V) to drop to
approximately 6V due to the resistance of the telephone line
60. The CPU 70 then causes the pre-recorded OGM message to
be played via the circuitry 80 and subsequently places the
TAD 20 in a mode to record any incoming message (ICM) onto a
resident storage device (not shown) via the record circuitry
50.
While the telephone call is being processed by the
TAD 20, the TAD 20 further monitors for a subsequent drop in
voltage on the telephone line 60 which would indicate that
the handset 40 or another telephone 90, connected to the same
telephone line 6D as the TAD 20, has gone off-hook. The
subsequent voltage drop is a result of a second loading on
the telephone line 60 caused by the telephone 90 or handset
40 being placed in parallel with the TAD 20. If a telephone
going off-hook is detected, the CPU 70 cancels any current
~007537
operations and places the TAD 20 in a stand-by mode. This
function is further explained in the following paragraphs.
When the TAD 20 is triggered by ringer signals
appearing on the leads TIP and RING the CPU 70 will place the
TAD 20 on-line (i.e. place the telephone line 60 in an off-
hook condition) to answer the call. This causes the voltage
on telephone line 60 to drop to approximately 6 volts. At
this moment the collector voltage of transistor Q2 is
approximately 6 volts (as transistor Ql has been placed in an
on state via the control signal on lead W, turning on
transistor Q4 and consequently transistor Ql), and con-
sequently capacitors C2 and C3 are charged to approximately 6
volts. Transistor Q7 is now turned off since the emitter-
base voltage of Q7 is 0 volts. This leads to zero voltage in
the base of transistor Q6, thus turning transistor Q6 off.
As a result, the collector voltage of transistor Q6 is
approximately at a nominal voltage Vcc of 5.4 volts. The
collector of transistor Q6 is connected to the CPU 70 via
lead Y which is used to activate a Calling Party Controller
(CPC) function of the TAD 20 which is capable of cancelling
the current call processing. Thus, when lead Y goes from
high to low, the CPU 70 will detect the falling edge and
activate the CPC function to thereby stop the operation of
the machine.
When the CPC function is activated the TAD 20 will
stop all operations (this includes outgoing message (OGM)
playing from the circuitry 80, incoming message (ICM)
recording via the record circuitry 50, fast forward (FF)
processing, or rewind (REW) processing) and go on-hook (which
disconnects the resistive load in the circuitry 80).
When any one of the telephones (such as shown by
telephones 40 or 90) are picked up, the voltage on telephone
line 60 will drop from the present 6 volts to approximately 4
volts, due to the increased loading on the line by the
telephone 40 or 90 and the TAD 20 being placed in parallel
across the telephone line 60. This causes capacitors C2 and
C3 to discharge. The RC time constants of capacitor C2 and
resistor R10, as well as capacitor C3 and resistor R13, cause
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the capacitors C2 and C3 to discharge at different rates. In
particular, the capacitor C2 discharges at a faster rate than
the capacitor C3, the time constants typically being 30
milliseconds and 100 seconds respectively. This causes a
voltage difference between the base and the emitter of
transistor Q7. When the voltage at the emitter-base of Q7
reaches 0.6 volts, the transistor Q7 is turned on, which
consequently leads to transistor Q6 turning on. At this time
the collector of transistor Q6 will go low from high, thereby
activating the CPC function. It is to be noted that diodes
D7, D8, and D9 provide isolation between the resistor/capa-
citor pairs R10/C2 and R13/C3.
When capacitors C2 and C3 have discharged, the
emitter-base voltage of the transistor Q7 is once again O
volts. This turns transistor Q7 off, which in turn causes
transistor Q6 to turn off. Transistor Q6 turning off causes
lead Y to return to a state of high potential, consequently
deactivating the CPC function of the TAD 20. At this point
the TAD 20 is returned to a state in which it may monitor for
any new incoming telephone calls. It is to be noted that
biasing for transistors Q6 and Q7 are provided by resistors
R14, R15, R16, and R17.
