CA1239236A - Time independent data transmission system - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A time independent data transmission system which allows a computer to access a remote data set at any time via non-dedicated telephone line is disclosed. The system is coupled to a telephone instrument, a data set and the telephone transmission line and normally connects the data set to the telephone transmission line. The telephone instrument is normally disconnected. In a preferred embodiment, a counting circuit senses the number of ring bursts in a ringing signal from a caller and a central computer is programmed to transmit a ringing signal having only one ring burst. When only one ring burst is sensed, the data set remains connected to the telephone transmission line and the data set begins to communicate with the central computer when the ringing signal terminates. If more than one ring burst occurs, a non-computer call is being sensed and the data set is disconnected and the telephone connected to the telephone transmission line so that normal telephone usage is allowed. Communication between the computer and the data set via the telephone line occurs without ringing the telephone instrument and without otherwise interfering with normal telephone usage. In the event the user wishes to use the telephone instrument at any time, including the time when communication between the computer and data set is taking place, a subscriber priority circuit allows the user to recouple the instrument to the line by merely lifting the telephone handset and to decouple the instrument by replacing the handset.

Description

¦¦ TIM~ INDEPENDENT DATA TRANSMISSION SYSTEM

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 3~
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 ~3~36 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.

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 ~ _7_ Yt,,~

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 ~L~3~
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 _9_ l ~3~6 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 3~
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 ~239~3~ 1 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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Claims (11)

WHAT IS CLAIMED IS:

1. An apparatus coupling a telephone data set and a telephone instrument to a telephone transmission line so as to enable the communication of data between the data set and a remote location without interfering with normal use of the telephone instrument, comprising:
first means, coupled to said telephone transmission line, said telephone instrument and said data set and normally connecting said data set to said telephone transmission line, for disconnecting said data set from said telephone transmission line and connecting said telephone instrument to said telephone transmission line in response to any of selected ones of a plurality of first electrical signals transmitted on said telephone transmission line, said first signals each being indicative of a call from a caller on said telephone transmission line, said first means preventing disconnection of said data set in response to a selected one of said first signals;
second means, coupled to said telephone transmission line and said data set, for detecting any of said first electrical signals transmitted on said telephone transmission line without answering the call and for generating a second electrical signal when any of the first electrical signals on said telephone transmission line has terminated, indicating that the caller has hung up;
said data set being adapted to communicate data via said first means in response to the generation of said second electrical signal after said selected one of said first electrical signals has terminated.

2. The apparatus recited in claim 1, further comprising third means, coupled to said data set, said telephone instrument and said telephone transmission line, for connecting said telephone instrument to said telephone transmission line and disconnecting said data set from said telephone transmission line in response to a first electrical signal generated by said telephone instrument, and for disconnecting said telephone instrument from said telephone transmission line and reconnecting said data set to said telephone transmission line in response to a second electrical signal generated by said telephone instrument.

3. The apparatus recited in claim 2 wherein said first means comprises first switching means coupled to said telephone instrument, said telephone transmission line and said data set and normally connecting said data set to said telephone transmission line.

4. The apparatus recited in claim 1 wherein each of said plurality of first electrical signals transmitted on said telephone transmission line comprises a ringing signal having varying number of ring bursts, and wherein said second means generates said second electrical signal when the transmission of said ringing signal on said telephone transmission line terminates.

5. The apparatus recited in claim 4 wherein said selected one of said first electrical signals is a ringing signal having a single ring burst, said first means preventing disconnection of said data set when said ringing signal having single ring burst is detected.

6. The apparatus recited in claim 4 wherein said second means comprises:
induction means coupled to said data set;
a source of voltage coupled to said induction means;
and second switching means coupled to said telephone transmission line and said source of voltage, and responsive to said ringing signal, for connecting said source of voltage to said induction means when said ringing signal is present on said telephone transmission line and for disconnecting said source of voltage from said induction means when said ringing signal terminates, said induction means generating said second electrical signal when said source of voltage is disconnected.

7. The apparatus recited in claim 3 wherein said first electrical signals each comprise ringing signals having a varying number of ring bursts and said first means further comprises counting means for sensing the number of ring bursts in said first electrical signals and for preventing disconnection of said data set from said telephone transmission line if the number of ring bursts is one and for disconnecting said data set from the telephone transmission line if the number of ring bursts is greater than one.

8. The apparatus recited in claim 7 wherein said counting means comprises resistor-capacitor circuit means for charging to a first voltage if only one ring burst occurs and for charging to a second higher voltage if more than one ring burst occurs, and threshold sensitive means responsive to a voltage at least as high as said second voltage, said threshold sensitive means being coupled to said first means and causing said first means to disconnect said data set from the telephone transmission line when said resistor capacitor circuit means charges to at least said second voltage.

9. The apparatus recited in claim 3 wherein said third means includes said first switching means normally connecting said telephone transmission line to said data set, and circuit means, coupled to said first switching means and said telephone instrument, for generating first and second electrical signals and being responsive to said first and second signals generated by said telephone instrument, said first switching means being responsive to said first and second signals generated by said circuit means and disconnecting said data set from said telephone transmission line and connecting said telephone instrument to said telephone transmission line in response to said first signal generated by said circuit means and connecting said data set to said telephone transmission line and disconnecting said telephone instrument from said telephone transmission line in response to said second signal generated by said circuit means.

10. The apparatus recited in claim 9 wherein said first signal generated by said telephone instrument is generated when the telephone receiver is lifted, and said second signal generated by said telephone instrument is generated when the telephone receiver is replaced.

11. The apparatus recited in claim 10 wherein said first and second signals generated by said telephone instrument comprise pulse signals of opposite polarity and said circuit means includes pulse discrimination means for discriminating between said pulse signals generated by said telephone instrument.