Note: Descriptions are shown in the official language in which they were submitted.
¦¦ TIM~ INDEPENDENT DATA TRANSMISSION SYSTEM
1 BACKGROUND OF THE INVENTION
2 1. Cross Reference to Related A~plication
This application for p~tent i~ related to prior
4 U.S. patent No. 4,469,917 entitled Time Synchronized
~ Data Transmission System.
6 2. ield_of the Inyen~tion
~ The present invention relates generally to telephone
8 data transmission systems, and more particularly to a time
9 independent data transmission system which allows a central
computer, for example, to access at any time a remote data
11 set, such as an electronic publication storage device, a
1~ hybrid telephone-cable television polling system, or a
13 computer data base &ubscriber's data set, via non-dedicated
14 telephone lines and communicate with that data set without
interfering with normal use of the subscriber ' 5 telephone.
16 The pre~ent invention finds application in many areas, one of
17 which, for instance, might be a sh~p-by-computer system where
18 it might be necessary to transmit information to and from an
19 individual subscriber's data set connected to an inf~rmation
storage device. Another might be the field of power demand
21 ~ data retrieval, wherein a central computer accesses a remote
22 data set which h~s stored therein data corresponding to the
23 electrical or other power consumed at the remote location.
24 Still another might be remote control of heating, ventilating
and air conditioning e~uipment through telephone lines.
26 Althouyh the invention will be des~ribed fvr use with
27 telephone lines, it will be apparent to one skilled in the art
28 that the invention can also be used with transmission media
t9 other than telephone lines.
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1 3. pescripti~n of the Pri~r Art
2 Various systems are presently known ~lhich allow
3 central computers to access individual subscriber's data sets
4 via dedicated telephone lines. For example, see U.S. Patents
S Nos. 4,126,762, 4,104,486, 4,394,540 and 4,345,113. In the
6 '486 and '540 patents r the telephone is isolated from the
7 telephone line during a selected time window. In the '762
8 patentr in one embodiment, a time window is utilized. In
9 another embodiment, sequential ringing signals having a
different time spacing than signals from a normal telephone
11 call condition the remote terminal to intercept the ringing
12 signals and to provide selective connection of a data
13 accumulator to the telephone line. It is preferable to use
14 the subscriber's existing telephone line rather than install a
separate dedicated line to provide access to the data set.
16 Thus, systems of this type require that the telephone line be
17 available for both use by ordinary persons and by computers
18 calling the subscriber. Requirements of systems of this type
19 are that when computer calls are received the call is
automatically transferred to a data set and the telephone
21 preferably should not ring.
22 In applicant's prior U.S~ Patent 4,345,113, an
23 automatic telephone message interception system is described
24 which permits the use of a single telephone line for both
~rdinary personal use and for receiving calls from a computer,
~6 wherein computer calls are automatically transferred to the
27 subscriber's data set without ringing the subscriber's
28 telephone. An ordinary ~non-computer) call made to the
29 ~ubscriber, would, however r be answered by the automatic
telephone message interception system described in this U.S.
1 Patent even if no one were present at the subscriber's
2 telephone. The caller ~ould thus be charged for a brief call ~.
even though no one answered the phone.
4 The sub~criber could, of course, solve this problem
by shutting off the automatic system if the telephone is to be
~ left unattended, but the data set could not be accessed by the
7 computer while the system was shut off.
8 The need thus existed or a system which both allows
9 a central computer to ascess the subscriber's data set via a
non-dedicated telephone line and which allows normal operation
11 of the telephone by both the subscriber and other persons
12 calling the subscriber. In particular~ such a system should
13 allow a computer to access the subscriber's data set without
14 ringing the subscriber's telephone and should allow perqons to
call the subscriber at any time without being charged for the
16 call if the telephone is unanswered.
17 In applicant's prior V.S. patent No. 4,469,917,
18 an apparatus which satisfies the above need is
19 described.
In that patent application, however, a system and
21 ~ apparatus i5 described for connecting a central computer to a
22 remote subscriber's data set using the subscriber's non-
?3 dedlcated telephone line during a preselected window in time.
24 In the present application, the apparatus described in that
patent applioation has been modified to permit ~onnection of
26 the centr~l computer at any time to a remote subscriberls data
27 set using the subs~riber's non-dedicated telephone line and
28 without interference of any sort with the normal use of the
29 ~subscriber's telephone. In the system described in the above
U.S. patent No. 4,469,917, the apparatus det cts A
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1 ringing signal on the telephone line during a preselected
2 window in time during which the subscriber's data set is
3 connected to the telephone line and the subscriber's telephone
4 instrument is disconnected. ~he apparatus does nothing until
the ringing signal stopsl indicating ~hat the caller has hung
6 up. The apparatus then causes the data ;et to dial up the
7 central computer and proceed to transmit or receive data
8 during the time window.
9 Accordingly, the need exists for a system which
ln allows a central computer to access a subscriber's data set
11 via non-dedicated telephone lines at any time (i.e., no
12 limitation to a time window)O Furthermore, such a system
13 should allow normal operation of the telephone by the
14 subscriber without interference in any way with the
subscriber's use of the telephone at any time, i.e., the
16 subscriber's telephone should not ring when the central
17 computer calls, the subscriber should be allowed to use the
18 telephone even if data transmission with the computer is
19 occurring and outside callers should not be charged for calls
when the phone is unanswered, for example.
21 ~ SUMMARY OF THE INVEMTION
22 It is therefore an object of the present invention
23 to provide an improved automatic data transmission system
24 which allows a central computer to access the subscriber's
data set at any time.
~6 It is a further object of the invention to provide
27 an automatic data transmission system which allows normal use
28 ~f the subscriber's telephone by the subscriber at all times.
29 Another object of the invention is to provide an
~utomatic data transmission system in which a central computer
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1 accesses the subscriber~s data set without disturbing the
2 subscriber in any way~
3 A still further object of the invention is to
4 prevent persons calling the subscriber from being charged for
the call when the telephone is not answered by the subscriber.
6 A yet further object of the present invention is to
7 provide a data transmission system which automatically
8 transfers calls from human callers to the telephone
9 instrument, allowing the telephone to ring, and which prevents
calls from a computer from ringing the telephone.
11 These and other objects of the present invention are
12 achieved by an apparatus coupling a telephone data set and a
13 telephone instrument to a telephone transmission line so as to
14 enable the communication of data between the data set and a
remote location without interfer.ing with normal use of the
16 telephone instrument, comprising first means, coupled to the
17 telephone transmission l.ine, the telephone instrument and the
18 data set and normally connecting the data set to the telephone
19 tansmission line, for disconnecting the data set from the
telephone transmission line and connecting the telephone
21 instrument to the telephone transmission line in response to
22 any of selected ones of a plurality of first electrical
23 signals transmitted on the telephone transmission line, the
24 first signals each being indicative of a call from a calle~ on
the telephone transmission line, the first means pre~enting
26 disconnection of the data set in response to a selected one of
27 the first signals, second means, coupled to the telephone
28 transmiss.ion line and the data set, for detecting any of the
29 first electrical signals transmitted on the telephone
transmission line without answering the call and for
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1 generating a second electrical signal when any of the first
2 electrical signals on the telephone transmission line has
3 terminated, indicating that the caller has hung up, the data
4 set being adapted to communicate data via the first means in
response to the generation of the second electrical signal
6 after the selected one of the first electrical signals has
7 terminated.
8 According to a preferred embodiment of the
9 invention, the apparatus is connected to the telephone line
at all times and the subscriber's telephone instrument is
11 always disconnected unless the subscriber regains control of
12 the line by lifting the receiver. When the central computer
13 calls the subscriber's telephone number, the computer allows
14 ~nly one ring before it hangs Up. The apparatus, having
~etected one ring, and waiting a suitable period of time,
16 detects no further rings, causes the data set to dial up the
17 central computer. If, however, a second ring follows the
18 ~irst ring, the apparatus transfers the telephone line to the
19 subscriber's telephone instrument which proceeds to ring and
~an be used nvrmally. The subscriber can gain direct control
21 ~f the telephone line at any time by lifing the receiver of
2~ his telephone inst,ument.
23 Other objects, features, and advantages of the
24 ~resent invention will be apparent from a reading of the
~etailed description which follows.
26 3RIEF DESCRIPTION OF THE DRAWINGS
27 The above objects and other novel features and
28 ~dvantages of the invention will be described in greater
29 ~etail in the following detailed description with reference to
he dr~wing fi~ures in which:
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1 ~ig. 1 is a schPmatic diagram of one
2 embodiment of a time independent data tran~mission system
3 according to the present inven~ion; and
~ Fi~. 2 illustrates graphically the operation
of part of ~he apparatus of Fig. 1.
6 DETAILED D~SCRIP~ION
7 With reference now to the drawings, a time
8 independent data transmission system i5 shown schematically in
9 Fig~ 1. A central computer may ~ccess each sub~criber's data
set 10 at any time through each ~ubscriber'~ telephone line,
11 indicated by reference numeral 2D. The central c~mputer is
12 prefe~ably programmed to provide only one ringing signal or
13 ring burst over the telephone transmission line, although, ~wo
14 or three rings could probably be used, ~ince very ew human
callers only allow two or three rings before hanging up. In
16 the preferred embodiment, if only one ringing signal is
17 detected, the subscriber's data set will be triggered to
18 dial-up the central computer and communicate with the
19 computer. Two-way communic2tion is contemplated, i.e., the
data set may, for example, both receive data from the computer
21 ~ ~nd transmit data to the computer. Additionally, the
22 subscriber may regain use of the telephone instrument during
~3 data transmission simply by lifting the telephone receiver.
24 The apparatus of the present invention may be
similar to the apparatu~ described in the above U.S.
26 patent No. 4,469,917. Since operation during a
27 preset time interval is not contemplated, no clock and
2~ associated clock-driven switching circuitry i5 necessary.
29 In~tead, data set 10 is normally connected to the telephone
line 20 through a first dual set of con~aets 60 (a and b) of a
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1 relay 61. A ring signal counting circuit 80 is coupled to the
2 telephone line 20 as shown. If counting circuit 80 detects
3 1 the commencement of a second ring burst, it triggers the latch
4 coil 62 of the relay 61 and thus connects the subscriber's
S telephone instrument 40 to the telephone line by allowing
6 contacts b and c of contacts 60 to make. The data set is thus
7 disconnected. The subscriber~s telephone instrument then
8 proceeds to ring and can be used normally. If a second ring
9 burst does not follow the first ring burst, the data set
lQ remains connected to the telephone line and is caused to dial
11 up the central computer~ as described in more detail below.
12 Ring signal counter 80 resets itself after each call. After
13 any use of the telephone lnstrument has been completecl the
14 data set is once more connected to the telephone line by the
relay 61 which has been unlatched by the operation of the
16 subscriber priority circuit 34, to be described in more detail
17 below. Thus~ for selected ones of the ringin~signals having
18 more than one ring burst, the data set is disconnected and the
19 telephone instrument connected. For a selected one of the
rinying signals, i.e., preferably a ringing signal having only
21 one ring burst, the data set remains connected and the tele-
22 phone disconnected.
23 The ring signal counter 80 essentially may be an RC
24 circuit disposed across the telephone line as shown in FIG. 1
comprising resistor R, capacitor C, diode D, resistor BR and
26 gas discharge tube GT. The time constant is chosen to charge
27 the capacitor C through resistor R and diode rectifier D to
28 approximately one-half of the ring signal voltage on the first
29 ring and to a higher voltage on the second ring as shown in
Fig. 2. The higher voltage is sufficient to trigger a gas
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ischarge tube GT in series with the latch coil 62 of relay
2 ~1, thus energizing the latch coil and connecting the
3 ¦~elephone instrument to the telephone line while disconnecting
4 ~he data set from the telephone line. A diode 84 is placed
between the pulse amplifier and shaper 35, to be described
6 below, and the latch coil 62, to prevent pulses from the
7 circuit 80 from feeding back into circuit 35. A high
8 resistance bl~eder resistor BR discharges the capacitor slowly
9 ~fter each single-ring call from the central computer. Other
vpes of counting circuits could obviously be used for this
11 purpose. For example, the gas discharge tube could be replaced
12 by semiconductor devices, e.y., a threshold sensitive zener
13 diode in series with a resistor coupled across the resistor
14 BR, the junction of the zener diode and the resistor being
coup.led to the base of a switching transistor having its
16 emitter-collector path in series with latch coil 62.
17 Furthermore, other circuits could be used, such as filter
18 circuits and appropriate digital logic counters.
19 ¦ The device shown in Fig. 1 further includes a ring
1 detector and trigger circuit 50, the operation of which will
21 . now be explained. When the central computer callsl or if
22 anyone else calls, the ring signal on the telephone line will
23 charge capacitor 36 through rectifying diode 38 and isolating
24 resistor 42. Contacts 44 operated by relay coil 46 of relay
45 will therefore close once relay coil 46 is ener~ized.
26 ¦ Resistor 48 and capacitor 36 have a time constant chosen so
27 ! ~.hat capacitor 36 remains sufficiently charged be~ween
28 successive rings of the same call and coil ~6 remains
energized. ~hen the caller hangs up and the ringing stops,
capacitor 36 will slowly discharge through resistor ~8 and
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1 coil 46 until relay 45 becomes deenergized, opening contacts
2 44. A voltage source 54 and an inductor 52 in series are
3 disposed across contacts 44. When contacts 44 open, a voltage
4 pulse is induced across inductor 52. This pulse is coupled
through diode 5~ to the data set 10 to trigger the data set's
6 ¦dial-up function. Diode 56 insures that only pulses of the
7 ¦proper polarity are coupled to the data set. Thus, the
8 ¦opposite pulse induced across inductor 52 when contacts 44
9 close will not be coupled to the data set. The data set 10
can then dial up the central computer through output llnes 58
11 which are used both for dial-up routines and for data
12 transmission and through dual pairs of contacts a and b of
13 contacts 60 of relay 61 controlled by relay coils 62 and 64.
14 The operation of relay coils 62 and 64 will be described in
lS more detail later with reference to the subscriber priority
16 circuit 34. At the time that the data set 10 initiates the
17 dial-up routine and when the telephone handset is down, the
18 pairs of contacts a and b of contacts 60 will remain made so
19 long as the central computer called ~only one ring signal
detected by ring signal counter circuit 80), so that the data
21 set output }ines are connected to the telephone line 20 and
22 the central computer can be dialed up and communication
23 between data set and computex can occur.
24 The embodiment of ring deteotor and trigger circuit
50 shown in Fig. 1 i~ only one orm of the circuit. Relay 4S
26 ould be replaced by a switching transistor, for example, and
27 the inductor 52 and related circuitry could be replaced by a
28 3ingle shot or monostable multivibrator triggered to output a
29 ?ulse when the switching transistor is biased off when the
3~ ringing signal terminates. I
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1 ¦ Should a non-computer call (i.e., more than one ring
2 signal) be received, the data set 10 will attempt to dial-up
3 the computer even though the computer did not Gall. Because,
4 however, contacts pairs a and h of relay contacts 60 have
opened, no such dial up signal will be transmitted to the
computer. Should a single ring signal be received which was
7 not generated by the central computer, the central computer
8 can be programmed so that it would ignore the return call
9 because it did not call the data set.
lD The data set can be any of many commercially
11 available devices. For example, if the system of the
12 invention is used to obtain data regarding the electric power
13 used by a consumer,-it mi~ht comprise a Power Demand
14 Accumulator Model 2000 Series manufactured b~ Fairchild Space
and Electronics Company. The present invention would allow
16 such a device to be coupled to the consumer's normal telephone
17 line and allow power meter readings to be read over the
18 telephone line.
19 The subscriber priority circuit 34 mentioned earlier
is designed to re-connect the telephone instrument 40 to the
21 - telephone line 20 when it is normally disconnected if the
22 subscriber lifts the telephone handset to use the phone.
23 Normally, the telephone instrument is disconnected from the
24 telephone line 20 by contacts 60, which also form a part of
circuit 34. The telephone, however, is also connected to the
26 pulse amplifier and shaper 35 of subscriber priority circuit
27 34 via voltage source 70 and resistor 72. rhe impedance
28 looking into resistor 72 and source 70 is chosen so that it
29 does not interfere with normal telephone use. When the
telephone handset is lifted, a voltage pulse of a particular
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1 ~ polarity appears across resistor 72. This pulse energizes
2 latch coil 62 of relay 61 through pulse amplifier and shaper
3 35 and connects the telephone instrument through contacts b
4 and c of contact set 60 of relay 61 to the telephone line 20,
while disconnecting the data set from the telephone line by
6 opening normally closed contacts _ and b of contact set 60 of
7 1 relay 61. When the subscriber replaces the telephone handset
8 t"hangS up"), a pulse of opposite polarity to the previous
9 pulse energizes unlatch coil 64 of relay 61 and opens contacts
b and c and closes contacts a and b, thus reconnecting the
11 data set to the telephone line and disconnecting the telephone
12 instrument from the telephone line. ~he pulse amplifier and
13 shaper circuit therefore performs the dual function of shaping
14 the pulse at its input and discriminating between positive and
negative pulses so as to energize the proper relay coil 62 or
16 64. Pulse amplifier and shaper 35 may take the Porm of
17 various circuits known in the art.
18 Although the invention as shown in the drawing
19 figures indicates discrete components, and schematically
indicates some electromechanical relays and switches, it is
21 - clear that the system can be constructed utilizing discrete
22 semiconductor devices or embodied in a solid state, integrated
23 circuit produced on a silicon or similar chip. For example,
~4 the function of the electromechanical relays which are
schematically indicated in the figure could be performed by
26 switching transistors.
27 In the foregoing specification, the invention has
28 been described with reference to a specific exemplary
29 embodiment thereof. It will, however, be evident that various
~odifications and changes may be made thereunto without
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1 ¦ departing from the broader spirit and scope of the invention
2 as set forth in the appended claims. The specification and
3 drawings are, accordingly, to be regarded in an illustrative
B rather than in restrictive sense.
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