CA1319769C - Digital added main line system - Google Patents

Abstract

DIGITAL ADDED MAIN LINE SYSTEM

ABSTRACT OF THE INVENTION
A method and apparatus for transmitting and receiving multiple telephone transmission signals over a single twisted pair. An analog signal from a local switching station is converted to an 80 kbits/sec signal for transmission over a twisted pair. A remote terminal converts the 80 kbits/sec signal back into a conventional analog signal for use in conventional telephone, facsimile or other related equipment.

WP50/13009/001.APP

Description

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DIGITAL ADDED MAIN LINE SYST~M

COPYRIGHT NOTICE
A portion o~ the disclosure of this pat~nt document contains material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND OF THE INVENTION
The present invention relates to the ~ield of telephone communication. More particularly, in one embodiment the present invention provides a me~hod and apparatus for simultaneously transmitting information from multiple phone connections over a single twisted pair line.
Techniques for transmission of multiple voice or data signals over a single phone line are well known in the telecommunications industry and are commonly referred to as concentration techniques; In the past, frequency division multiplexing was the most commonly used technique for simultaneous transmission of multiple voice or data signals over a single line. Frequency multiplexing techniques are still commonly used in, for example, wideband transmission media.
Digital time division multiplexing techniques have been used since the 1960's and have become the most common concentration technique in, for example, inter-office circuits. An entire family of T-carrier (Trunk carrier) systems such as Tl, TlC, TlD, T2, and T4, have been developed for concentration of mul~iple voice and data signals over a common line. Digital concentration techniques are described in, for example, Bellamy, Diaital Telephony, Wiley and Sons, 1982, which is incorporated herein by reference for all purposes.
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Digital communication has become relatively standard in, for example, intraoffice trunks. One example of a method for transmitting multiple voice or data signals over a single two- or four-wire transmission line is disclosed in Kaiser et al., "Digital Two Wire Local Connection Providing Office Su~scribers With Speech, Data, and New TeleinformatiOn Services," ISSLS, March 20-24 (1978)~ In ~aiser et al., telephone data, viewdata, telecopier information and the like are transmitted in a digital fashion over a two- or four-wire line to a local exchange. Digital data are transmitted in data bursts which are later expanded and recovered using, e.g., time division multiplexing techniques.
Despite advances in the multiplexing techniques a variety of problems remain. For example, some multi-plexing techniques continue to require complex and, therefore, uneconomical equipment. This equipment is particularly unsuitable for individual or small office users. Further, when applied to residential users, small office users, and the like, some systems require that the user provide a power source such as a transformer con-nection to a 120 v. power source, a battery power source or the like. Some systems require that the user replace existing two-wire connections with less conventional connections and/or are limited in the distance of twisted pair line over which information may be transmitted. In spite of certain advances in the ability to transmit multiple voice and data signals over single twisted pairs, most local switching units continue to provide a single analog signal over a single twisted pair to a typical home or office.
It would be desirable to provide an improved ; and more economical method and associated apparatus for multiplexing multiple phone line connections over a single twisted pair connection especially for use in providing multiple phone lines over a single twisted pair into a home or office from a local telephone exchange.

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SUMMARY OF THE INV~:NTION
An improved method and apparatus for transmission of multiple signals over a single twisted pair is disclosed. In a preferred embodiment the invention provides for transmission of multiple voice and/or data signals over a single twisted pair from a local telephone exchange to a subscriber.
In one embodiment, the invention provides apparatus for concurrently receiving "n" telephone signals over a twisted pair, where "n" is greater than 1, comprising at a first location, means for receiving a digital signal from a local telephone exchange, the digital signal representing said "n" telephone signals in digital form; means for converting the digital signal into a first higher-rate binary signal; and means for converting the higher-rate binary signal into "n" analog signals for use in equipment at said first location. The digital signal may, for example, be a 4B3T or quaternary signal.
A method of transmitting "n" telephone signals over a twisted pair from a first location is also pro-vided. The method includes the steps of converting "n"
analog telephone signals to a binary signal; converting the binary signal to a lower-rate digital signal; and transmitting said lower-rate digital signal over said twisted pair to a second location. In an alternative embodiment, the method includes the steps o~ inputting a digital signal from a second location over a twisted pair to a first location; converting the digital signal to a higher-rate ~inary signal and converting the higher-rate ~inary signal to "n" analog signals for use in telephone equipment at the first location.
~ kit for concurrent transmission of a plural-ity of telephone signals over a single twisted pair froma subscriber location to a local switching station is also provided. The kit includes master equipment in-:

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cluding a means for conversion of quaternary 80 kbits/secsignals to and from a higher-rate binary data stream; a SICOFI for conversion of the binary data stream from and to analog signals; and remote terminal equipment includ-ing a means for conversion of quaternary 80 kbits/secsignals from and to binary higher-rate data streams; a means for conversion of binary higher-rate data streams from and to analog signals and a means for two-wire to four-wire conversion.

BRIEF DESCRIPTION OF THE FIGURES
Fig. 1 is an overall block diagram of a remote terminal (RT) according to one embodiment of the invention;
Fiy. 2 is an overall block diagram ~f a master according to one embodiment of the invention; and Fiys. 3a to 3e are block diagrams of the logic used in microprocessor in the RT.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

CONTENTS
I. General II. Digital Data Transmission A. Hardware B. Software/Microprocessor Functionality III. Power Management I. General An improved method and apparatus for transmit-ting and receiving data over a single twisted pair wire are disclosed herein. The method and apparatus will find particular utility and is illustrated herein as it is applied in the transmission of multiple voice, data, and 35 alarm signals over existing twisted pair lines which are used to connect homes, offices, and the like to local switchinq facilities, or central offices, but the , .

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invention is not so limited. The invention will find use in a wide variety of applications where it is desired to transmit multiple voice and/or data signals over a single twisted pair including, for example, facsimile, computer data, alarms, and/or low-speed video signals.

II. Diq tal Data Transmission A. Hardware Fig. 1 provides a block diagram of a remote terminal (RT) according to one embodiment of the invention. The RT would be placed in, for example, a home, office or other subscriber facility for trans-mission and/or reception of voice or data signals over a single twisted pair line l to and from a local telephone exchange. A plurality of phones or other subscriber equipment would utilize analog signals produced by the RT and provide analog signals to the RT for transmission over the twisted pair.
A siqnal DCL From Master enters or leaves the RT over the conventional two-wire line l, which may be the type commonly used in households, offices, or the like. As will be readily apparent to those of skill in the art, the signal could either be a transmitted voice or data signal from the master. The invention will be illustrated herein as it applies to the RT primarily with regard to an incoming signal, but the process is similarly applied in reverse to provide voice and data signals from the RT to the master.
The signal DCL From Master, representing in digital form a voice or data signal, enters a line transformer 2 for isolation and for impedance matching.
The voice or data signal entering the line transformer 2 is an 80 kbits/sec signal having one of four voltage levels. While the invention is illustrated herein with regard to the preferred 80 kbits/sec signal, it is believed that the invention herein would find utility using signals of between about 50 and 100, and preferably between 70 and 90 kbits/sec. The use of an 80 kbits/sec 2BlQ INSA line protocol signal permits the transmission and reception of voice and data signals over extended lengths of twisted pair wires, e.g., 1,000, 15,000, 20,000 feet or more, without smearing, i.e., signal quality over large distances is improved because the lower frequency 80 kbit signal may be more readily separated.
The signal from the line transformer enters an ISDN Echo Cancellation-Quaternary (IECQ) chip 4 via line 3a. The 80 kbit 2BlQ INSA line protocol signal contains 160 kbits/sec of information and the IECQ chip 4 converts the 80 kbits/sec signal into a 160 kbits/sec binary signal. The 160 kbits includes 16 kbits uf line control information and 144 kbits of user data. 112 kbits/sec of chip control information are added to the data stream by the IECQ chip, resulting in 256 kbits/sec data stream from the IECQ chip and provided to ISDN
Communications Controller (ICC) multiplexing and data handling chip 6 over line 5a. The ICC operates on a clock signal (CLK) at, for example, about 520 kHz and a ~rame control signal (FSC) at, for example, about 8 kHz.
CLK and FSC are provided over line 7.
Over a one-wire bus 13, the ICC chip 6 sends 8 bits of data on one channel, 8 bits of data on the other channel, 8 bits of control, and 8 bits of signal data to Codac Filter (SICOFI) 10, and then repeats, permitting substantially simultaneous transmission/reception of two or more voice or data signals. Monitor data, ring data, and other data which the microprocessor poles are also made available to the microprocessor.
SICOFI 10 converts the binary bits into analog signals in which both frequency and amplitude are modulated. The analog signals are then transmitted over line 9a to Subscriber Line Interface Circuits (SLIC's) 12a and 12b. SLIC's 12a and 12b are 4-wire to 2-wire converters and serve to increase the power available for utilization by the subscriber's phone or other communication device by enpressing the analog signal on high velocity DC. Conventional analog information is provided to subscriber phones 17a and 17b from the SLIC's over lines 14a and 14b.
Ring inserts 16a and 16b are relays which close when it is desir~d for a phone to ring under the direc-tion o~ the microprocessor. Power supply 18, using a process more fully described below, provides general power and ring power to the phones at appropriate times via a ring bus 20. Buffer 22 serves to interface local status and alarms.
Outgoing signals from the subscriber are processed in a similar but reverse method from incoming signals. In particular, analog signals enter SLIC's 12a and 12b for two-wire to four-wire conversion via lines 15. Signals from SLIC's 12a and 12b enter SICOFI 10 via lines 9b for analog-to-binary 8-bit word conversion.
These 8 bit words are, thereafter, converted in ICC 6 into a binary stream containing 160 kbits/sec of user information (144 kbits of user data plus 16 kbits of line control) for input to IECQ 4 via line 5b. IECQ 4 converts the 160 kbits/sec signal ~o an 80 kbits/sec quaternary signal for transmission to telephone company equipment over the twisted pair 1.
Fig. 2 is a block diagram of a master unit which would be placed in a local switching unit, central office, or other telephone company equipment at the terminus of a ~wisted pair wire 1 from a home, office or the like. The function of the master is similar to that of the RT , but reversed; i.e., the master converts conventional analog signals from local switch lines 50a and 50b to appropriate digital signals for transmission over the twisted pair and converts digital signals from the twisted pair to analog for transmission over local switch lines. Of course, the master is not generally power constrained (due to its location and lack of need '~ .

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to provide ring capability) and may function using a conventional 48-volt power supply 52 from the local switching unit.
Ring detects 54a and 54b detect an incoming ring signal from switch lines ~Oa and 50b by AC coupling.
When a ring is detected the microprocessor sends an appropriate ring signal in the line control data so as to ring a line at the RT.
Incoming analog signals enter SICOFI 56 from the switch lines via lines s5a where they are converted to digital, 8-bit words similar to those in the RT
described above. SICOFI 56 transmits to the ICC via bus 57. ICC 58 serves a multiplexing and data handling function similar to that of the ICC in the RT and transmits 160 kbits/sec of user information (144 kbits of user data plus 16 kbits of line control) to IECQ 60 via line 59a for conversion to 80 kbits/sec quaternary signals for transmission over twisted pair 1. The master similarly processes incoming digital information from the RT in a reverse order. Line transformer 61 also serves an isolation function, receiving signals via line 63a.
The functionality of the master is overseen by a microprocessor 60, similar to the RT. A clock 62 provides timing information for the microprocessor and the other components in master and, ultimately, the RT.
Buffer 64 serves to interface status and alarms. Bus 66 serves to provide an office system interface from system alarms.
Without in any way limiting the scope of the invention, Tables 1 and 2 provide a list of commercially available components which are useful in operation of the RT and Master respectively according to the above embodiments. It will be apparent to those of skill in the art that the components listed in Tables 1 and 2 are 35~ merely representative of those which may be used in association with the inventions herein and are provided for the purpose of fa~ilitating asser~ly of a device in ~ 3 ~

accord with the invention. A wide variety of components readily kno-~n to those of skill in the art could readily be substituted or functionality could be combined or separated. It should be noted that CMOS-based devices have been utilized where possible (e.g., the micro-processor) so as to reduce power consumption of the RT in particular.

Tabl _l RT Components Line Transformer 2 13 mh, 1:1.32 IECQ 4 Siemens 2091 ICC 6 Siemens 2070 Microprocessor 8 Intel 80C49, 80C51 or 87C51 SICOFI 10 Siemens 2260, or 2060 SLIC 12 Erickson PBL 3764, or Harris equipment Buffer 22 74HC244 -Table 2 Master Components Ring Detect 54 Siemens PSB 6620 SICOFI 56 Siemens 2260 or 2060 ICC 58 Siemens 2070 IECQ 60 Siemens 2091 Clock 62 74HC4060 Microprocessor 60 Intel 80C51, 87C51 or 8048 - 10 ~3~
B. Software/Mic~cprocessor Functionality Appendix I provides an assembly language program listing (Copyright, Unpublished Work, Raychem Corporation) for the RT microprocessor 8 discussed above.
TAe code is adapted for and has been used on an Intel 80C51 microprocessor, although it will be apparent that the invention could be applied to a wide variety of such processors. Appendix II (Copyright, Unpublished Work, Raychem Corporation) provides a similar listing for the code used in the microprocessor 60 in the master. This code has been used in the Intel 80C51. Again, however, a wide variety of microprocessors could be used herein without departing from the scope of the invention.
Figs. 4a to 4e are flow charts illustrating the functionality of the software used in the RT and Master, and provide an overview of the software in Appendix 1 and Appendix 2. The left hand portion of Fig. 4a illustrates the power-up se~uence used to initiate the system. The system begins by resetting the microprocessor (8051) registers and memory. The ISDN chip 2, the ICC, SICOFI's, and the like are reset and configured.
Variables within the program are, thereafter, activated, timers are started, and 160 Hz interrupts are started.
The program then enters a main loop, which is illustrated in detail beginning on the right half of Fig. 4a.
Upon receiving a 160 Hz clock interrupt, the system reloads the clock counter and, in the RT, reads any local alarms (such as alarms from a burglar alarm and the like). The system then reads the local hook status and determines if a message has been transmitted over the link from the RT/Master. If a message has been ~ransmitted over the link, the system reads the message to determine the hook status (i.e., on or off hook) and any alarms. If there is not a message from the other end of the link, the system determines if it has made more than a preset number of passes without a message from the other end of the link. If so, the tolerance count of - -consecutive messages missed is reset and an alarm is set which may be, for example, passed off to a CO.
In any event, the system then goes on to determine if it is ready to transmit across the link by checking a flag in the ICC. If not, a similar test and reset procedure is followed to that described above for receiving messages. If the link is ready to transmit, the messages are loaded and sent to the RT/Master from the Master/RT.
Referring to Fig. 4b, the system then determines if there has been any change in the command/instruction (C/I) channel from the SICOFI.
If not, the system determines if the link is down and, if not, continues on. If the link is down, the system compares the number of passes to a limit and, if the link has been down for greater than that limit, resets a link missing tolerance count and issues a command to reactivate the link.
If there has been a change on the C/I channel, the system then determines if the change has been an activation indication. If not, the system determines if the link was previously up and, if not, the loop continues. If the link was previously up, the SICOFI in the RT is powered down, and the hook and alarm data for the far end are reset. An indication is also provided to the user that both lines are down and the alarms are on.
The missing tolerance count is reset and a command is then issued to reactivate the link.
Referring to Fig. 4e, if the change on a C/I
channel was an activation indication, the High-Level Data Logic Control (HDLC) transmission mode is set, the link transmitter and receiver are reset, and an indication is provided that the link is up. The system then continues through the main loop.
In the master (or "COT" end) the main loop then determines if the off hook or local line request for line is received. If so, an indication is provided at the , 12 ~ ~197~
Master that line A is off the hook. A similar test is provided for line B and displays are provided on LED's.
The system then determines, for both lines, if the line is off the hook. For either line which is off the hook, a line is seized at the COT. The clock interrupt routine is then exited at the Master.
Referring to Fig. 4d, the main loop in the RT
continues by copying the local hook status and far-end ring request to line status bytes. Line service routines for both lines are called and the clock interrupt routine is exited.
Fig. 4e illustrates the line service routine for the RT. A test is first conducted to determine if the RT is in a ring stop mode. If so, a test is conducted to determine if a ring stop period has expired and, if so, the ring stop mode is cleared and the ring relay is deactivated. The system then returns to the main loop.
If the system is not in a ring stop mode, it is determined if a ring is requested. If a ring is requested, but the line is off the hook, the SICOFI is powered down to conserve power, and the line service routine is exited. If the line is not off the hook, it is determined if the line is in the ring-active mode and, if so, a ring oscillator is toggled and the line sérvice routine returns to the main loop. An intermediate test is conducted, however, to determine if the other line is off the hook. If not, the ring relay is activated.
However, if the other ring is in the ring-active mode, the system returns to the main loop.
If a ring has not been requested, the line is not in the ring-active mode, and the line is not off the hook, the SICOFI is powered down and the system returns to the main loop. If, however, the line is off the hook, the ~ICOFI is powered up for conversation. If a ring has not been requested and the line is in the ring-active mode, the Fing stop ~ode is set and the ring oscillator , , ' -.

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is deactivated. The system then returns to tha main 1oop.

III. Power Manaqement The system described above provides multiple-line telephone services to a user over a single twisted pair without the need to provide a battery or other current source at ~he RT. At the same time, the system maintains the line power within the limits proscribed by TR-TSY-000057 standard AII in a standby mode and AIII
during active line use.
Table 3 illustrates the power usage of the varlous components in the system in a standby mode, an active mode, a l-ring mode, and a 1-active, l-ring mode.
The data illustrated in Table 3 are based on a 16500-foot twisted pair using 26-gauge wire plus 1500 feet of 24-gauge wire.
Table 3 illustrates that by use of the method/
apparatus disclosed herein, in the standby mode the system is well within AII limits. Specifically, about 430 milliwatts may readily be provided in a typical system while remaining in AII limits, while only 373 milliwatts are needed during standby. Similarly, the 2302 milliwatts needed for 1-ring and l-active signals are well within the amount of power which may be provided while staying within AIII limits.

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Table 3 System Power Use (milliwatts) Mode ComponentStandby 2-Active 1-Ring 1-Active.1-Ring Microprocessor 25 25 25 25 Loop 01176 0 588 Ring o o 1200 1200 TOTAL: 3731714 1690 2302 It is to be understood that the above descrip-tion is intended to be illustrative and not restrictive.
Many embodiments will be apparent to those of skill in the art upon reviewing the above description. By way of example the inventions herein have been illustrated primarily with regard to transmission of voice and data signals (POTS), but they are not so limited. For example, the inventions could be applied in the trans-mission and reception of radio and TV signals, telephoto, ; 25 teletype, facsimile, and other signals. By way of further example, the inventions have been illustrated above with reference to the simultaneous transmission of two signals over a single twisted pair, but the inven-tions could readily be extended to transmit 3 or more signals simultaneously over a single twisted pair. The scope of the inventions should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

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Claims (31)

1. Apparatus for concurrently receiving "n"
telephone signals over a twisted pair, where "n" is greater than 1, comprising:
a) at a first location, means for receiving a digital signal from a local telephone exchange, said digital signal representing said "n" telephone signals in digital form;
b) means for converting said digital signal into a first higher-rate binary signal; and c) means for converting said higher-rate binary signal into "n" analog signals for use in equipment at said first location.

2. Apparatus as recited in claim 1 further comprising a master at a local telephone distribution point, said master converting "n" analog telephone signals from said local telephone distribution point to said digital signals for transmission over said twisted pair.

3. Apparatus as recited in claim 2 wherein said master further comprises:
a) means for converting at least "n" analog signals from said local telephone distribution point into a second higher-rate binary signal; and b) means for converting said second higher-rate binary signal into said digital signal.

4. Apparatus as recited in claims 1, 2, or 3 wherein said first location further comprises subscriber equipment.

5. Apparatus as recited in claim 1 wherein said means for receiving is a means for receiving a signal between about 70 and 90 kbits/sec.

6. Apparatus as recited in claim 1 wherein said means for receiving is a means for receiving a signal of about 80 kbits/sec.

7. Apparatus as recited in claim 1 wherein said higher-rate binary signal is a substantially 160 kbits/sec signal comprising user data.

8. Apparatus as recited in claim 1 further comprising means for transmitting a digital signal from said equipment at a first location comprising:
a) means for converting at least "m" analog signals, to third higher-rate binary signals, where "m"
is greater than 1;
b) means for converting said third higher-rate binary signal into a second digital signal; and c) means for transmitting said second digital signal to said local telephone distribution point.

9. Apparatus as recited in claim 8 wherein said third higher-rate binary signal is a substantially 160 kbits/sec binary user information signal and said second digital signal is an 80 kbits/sec signal.

10. Apparatus as recited in claim 9 wherein said digital signal and said second digital signal are quaternary signals.

11. Apparatus as recited in claim 1 further comprising means for removing at least a portion of said means for converting from service after a data transmission period.

12. Apparatus as recited in claim 1 wherein said twisted pair has a length greater than 1,000 feet.

13. Apparatus as recited in claim 1 wherein said twisted pair has a length greater than about 15,000 feet.

14. Apparatus as recited in claim 1 further comprising a subscriber line interface circuit, said subscriber line interface circuit converting said analog signals from a two-wire format to a four-wire format.

15. Apparatus as recited in Claim 14 wherein said first location is a subscriber location.

16. Apparatus for concurrent transmission of multiple telephone signals from and to a local telephone exchange to a subscriber location over a twisted pair line comprising:
a) a remote terminal at said subscriber location, said remote terminal comprising:
i) means for inputting and outputting a substantially 80 kbits/sec quaternary signal to and from said twisted pair;
ii) means for converting said 80 kbits/sec quaternary signal to and from a substantially 160 kbits/sec binary signal;
iii) means for converting said 160 kbits/sec signal from and to an analog two-wire signal; and iv) means for converting said two-wire signal to a four-wire signal for use by the telephone subscriber; and b) a master comprising:
i) means for inputting from and outputting to multiple analog telephone signals from a local switching facility;
ii) means for converting said analog signals to and from a 160 kbits/sec binary signal; and iii) means for converting said 160 kbits/sec signal to and from said 80 kbits/sec signal.

17. Apparatus for transmitting "n" telephone signals over a twisted pair comprising:
a) means for converting "n-" analog signals at a first location to a binary signal;
b) means for converting said binary signal into a lower-rate digital signal; and c) means for transmitting said lower rate digital signal over said twisted pair to a second location.

18. Apparatus as recited in claim 17 wherein said first location is a subscriber location and said second location is a local switch.

19. A method of transmitting "n" telephone signals over a twisted pair from a first location where "n" is greater than 1 comprising:
a) converting "n" analog telephone signals to a binary signal;
b) converting said binary signal to a lower-rate digital signal; and c) transmitting said lower-rate digital signal over said twisted pair to a second location.

20. A method for receiving "n" telephone signals over a twisted pair comprising:
a) inputting a digital signal from a second location over a twisted pair to a first location;
b) converting said digital signal to a higher-rate binary signal; and c) converting said higher-rate binary signal to "n" analog signals for use in telephone equipment at said first location.

21. The method as recited in claims 19 or 20 wherein said first location is a telephone subscriber location and said second location is a local telephone exchange.

22. The method as recited in claim 19 further comprising the steps of:
a) receiving said lower-rate digital signal at said second location;
b) converting said lower-rate digital signal to a second higher-rate binary signal; and c) converting said lower-rate digital signal to an analog signal for a local telephone exchange.

23. The method as recited in claim 19 further comprising the steps of:
a) at said second location, converting an analog signal to a second higher-rate signal; and b) converting said second higher-rate binary signal to said digital signal.

24. The method as recited in claims 19 or 20 wherein said binary signal is between about 70 and 90 kbits/sec.

25. The method as recited in claims 19 or 20 wherein said binary signal is about a 160 kbits/sec signal.

26. The method as recited in claims 19 or 20 wherein said digital signal is a quaternary signal of between about 70 and 90 kbits/sec.

27. The method as recited in claim 19 wherein the step of converting "n" analog telephone signals further comprises the step of converting from four-wire to two-wire format.

28. The method as recited in claim 20 wherein the step of converting to "n" analog signals further comprises the step of converting from a two-wire to a four-wire format.

29. The method as recited in claim 20 further comprising the step of removing a portion of a means for performing said step of converting said binary signal from service after a data transmission period.

30. A method of concurrently transmitting and receiving a plurality of telephone signals from and to a subscriber location from a local switching station over a single twisted pair, said local switching station adapted to transmit analog telephone signals, subscriber equip-ment at said subscriber location adapted to utilize analog signals, comprising the steps of:
a) in a master terminal at said local switching terminal:
i) converting first analog signals representing multiple telephone transmissions from said local switching station to substantially a first binary signal of about 160 kbits/sec;
ii) converting said binary signal to a first quaternary signal of about 80 kbits/sec;
iii) transmitting said first quaternary signal to said subscriber location over said twisted pair;
iv) receiving a second quaternary signal from said twisted pair;
v) converting said second quaternary 80 kbits/sec signal to a second binary signal of about 160 kbits/sec; and vi) converting said second binary signal to second analog signals for transmission to said local switching facility; and b) at a remote terminal at said subscriber location:
i) receiving said first quaternary signal from said twisted pair;
ii) converting said first quaternary signal to a third binary 160 kbits/sec signal;
iii) converting said third binary 160 kbits/sec signal to an analog, two-wire signal;
iv) converting said two-wire signal to a first four-wire signal for use in said subscriber equipment:
v) receiving a second four-wire signal from said subscriber equipment;
vi) converting said four-wire signal to a two-wire signal;
vii) converting said two-wire signal to a fourth binary 160 kbits/sec signal; and viii) converting said fourth binary 160 kbits/sec signal to provide said second 80 kbits/sec signal to said twisted pair.

31. A kit for concurrent transmission of a plurality of telephone signals over a single twisted pair from a subscriber location to a local switching station comprising:
a) master equipment:
i) means for conversion of quaternary 80 kbits/sec signals to and from binary signals; and ii) means for conversion of binary signals from and to analog signals; and b) remote terminal equipment including:
i) means for conversion of quaternary 80 kbits/sec signals from and to binary signals;
ii) means for conversion of binary signals from and to analog signals; and iii) means for two-wire to four-wire conversion.