Digital data transmission system

• US 4,302,629 A
• Filed: 08/01/1979
• Issued: 11/24/1981
• Est. Priority Date: 03/14/1979
• Status: Expired due to Term

• Current Assignee: Teltone Corp. (Capgemini SE)
• Original Assignee: Teltone Corp. (Capgemini SE)
• Inventors: Trombly, John E., Worthington, David K., Foulkes, John D.
• Primary Examiner(s): Popek, Joseph A.
• Application Number:
  US06/062,720
• Time in Patent Office: 846 Days
• Field of Search: 179/2 DP, 179/2.51, 179/16 F, 179/170 R, 370/26, 370/75, 370/97
• US Class Current: 370/483
• CPC Class Codes: H04L 27/122 using digital generation of carrier signals digital function generators G06F1/02, H04L17/10; generating pulses having stepped portions using digital techniques H03K4/026
• CPC Class Codes: H04L 5/06 the signals being represented by different frequencies combined with time-division multiplexing H04L5/26
• CPC Class Codes: H04M 11/062 using different frequency bands for speech and other data

Abstract

Simultaneous conventional telephone signaling and audio communication, plus digital data transmission, on nonloaded telephone wires is disclosed. Modems (21) connect a telephone (23) and a digital data terminal (25) to one end of the telephone wires. A data transmitter (59) in each modem (21) converts digital data from binary to FSK form and a receiver (57) converts digital data from FSK to binary form. Each transmitter includes a frequency synthesizer that produces one of two FSK signals (F1, F2) depending upon the binary nature (0 or 1) of a particular data bit; and, the receivers include frequency detectors that detect two other FSK signals (F3, F4) and produce a corresponding binary data bit (0 or 1). Voice filters (51) prevent the FSK data signals from reaching the telephones and spurious telephone high frequency signals from reaching the telephone wires. A CO or PABX subsystem (37) is connected to the other end of the telephone wires and includes modems comprising receivers (97) that convert the F1/F2 FSK signals into binary digital data. The binary digital data from the telephone stations is multiplexed and forwarded to a data processing center (15). The CO and PABX subsystem also de-multiplexes multiplexed binary digital data produced by the data processing center and includes transmitters (99) that convert the de-multiplexed data into F3/F4 FSK signals and forward the F3/F4 FSK signals to the related station. Voice frequency filters (91) prevents the FSK signals from reaching the CO or PABX line switching equipment and prevents high frequency noise signals generated by the CO or PABX from reaching the telephone wires.

Claims

1. In a transmission system for carrying baseband telephone signals, said transmission system including telephone switching equipment connected to telephones via nonloaded loops, the improvement comprising a digital data transmission system for carrying digial data over said nonloaded loops without interfering with the baseband signals carried by said nonloaded loops, said digital data transmission system comprising:

(A) station modems connected between telephones located in the vicinity of associated data terminals and the telephone end of related nonloaded loops running to said telephone switching equipment, said station modems also connected to said associated data terminal, each of said station modems including;

(1) transmitting means for converting digital data produced by said associated data terminal from binary signal form into FSK signal form such that a binary zero (0) causes said FSK signal to have a first frequency, F1, and a binary one (1) causes said FSK signal to have a second frequency, F2, and applying said F1 and F2 FSK signals to said related nonloaded loop;

(2) receiving means for receiving digital data carried by said related nonloaded loop in FSK signal form at third, F3, and fourth, F4, frequencies and converting said F3 and F4 FSK digital data into binary form such that an FSK signal at said third frequency, F3, causes a binary zero (0) and an FSK signal at said fourth frequency, F4, causes a binary one (1) and applying said binary digital data to said associated data terminal; and

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(3) voice filter means for connecting said related nonloaded loop to said telephone so as to prevent said F1, F2, F3 and F4 FSK signals from reaching said telephone; and

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(B) a switching equipment subsystem located in the vicinity of said telephone switching equipment and connected to the other ends of said nonloaded loops, said switching equipment subsystem comprising;

(1) modern means connected to the other ends of said nonloaded loops for;

(a) converting said F1 and F2 FSK signals applied to said nonloaded loops by said transmitting means of said station modems from FSK signal form into binary digital data form such that an F1 FSK signal causes a binary zero (0) and an F2 FSK signal causes a binary one (1);

(b) converting binary digital data received from a bidirectional signal forwarding means into FSK signal form such that a binary zero (0) causes said FSK signal to have said third frequency, F3, and a binary one (1) causes said FSK signal to have said fourth frequency, F4, and applying said F3 and F4 FSK signals to said nonloaded loops; and

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(c) voice filter means for connecting the other ends of said nonloaded loops to line switching equipment forming part of said telephone switching equipment so as to prevent said F1, F2, F3 and F4 FSK signals from reaching said line switching equipment; and

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(2) bidirectional signal forwarding means connected to said modem means for;

(a) receiving the binary digital data produced by said modem means resulting from the conversion of said F1 and F2 FSK signals from FSK signal form into binary digital data form and forwarding said binary digital data to a data processing center; and

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(b) receiving binary digital data produced by said data processing center and applying said binary digital data to said modem means for conversion by said modem means from binary digital data form into F3 and F4 FSK signal form.

2. The improvement claimed in claim 1 wherein said transmitting means of said station modems includes a frequency synthesizer for producing said F1 and F2 FSK signals in accordance with the binary form digital data produced by the associated data terminal and wherein said receiving means of said station modems includes a frequency detector for detecting said F3 and F4 FSK signals and converting said F3 and F4 FSK signals into binary form digital data and applying said binary form digital data to said associated data terminal.

3. The improvement claimed in claim 2 including an automatic gain control circuit connected between said receiving means and said transmitting means of said station modems such that the amplitude of the F1 and F2 FSK signals produced by said frequency synthesizers of said transmitting means is controlled by the negative logarithm of the amplitude of the F3 and F4 FSK signals received by said receiving means.

4. The improvement claimed in claim 3 wherein said modem means includes a plurality of subsystem modems, each of said subsystem modems including:

a transmitting means for converting binary digital data received from said bidirectional forwarding means into FSK signal form such that a binary zero (0) causes said FSK signal to have said third frequency, F3, and a binary one (1) causes said FSK signal to have said fourth frequency, F4, and applying said F3 and F4 FSK signals to a related nonloaded loop;

receiving means for receiving said F1 and F2 FSK signals applied to said related nonloaded loop by said transmitting means of a related station modem and converting said F1 and F2 FSK signals into binary digital data form such that an F1 FSK signal causes a binary zero (0) and an F2 FSK signal causes a binary one (1) and applying said binary digital data to said bidirectional forwarding means; and

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a voice filter for connecting the other end of said nonloaded loop to said line switching equipment.

5. The improvement claimed in claim 4 wherein said transmitting means of said subsystem modems includes a frequency synthesizer for producing said F3 and F4 signals in accordance with the binary form digital data received from said bidirectional forwarding means and wherein said receiving means of said subsystem modems includes a frequency detector for detecting said F1 and F2 FSK signals and converting said F1 and F2 FSK signals into binary form digital data and applying said binary form digital data to said bidirectional forwarding means.

6. The improvement claimed in claim 5 wherein said bidirectional forwarding means comprises a multiplexer/demultiplexer for multiplexing the binary digital data produced by said receiving means of said subsystem modems and forwarding said multiplexed binary digital data to said data processing center and for receiving multiplexed binary digital data produced by said data processing center, demultiplexing said binary digital data produced by said data processing center and applying demultiplexed binary digital data to said transmitting means of said subsystem modems.

7. The improvement claimed in claim 1 wherein said modem means includes a plurality of subsystem modems, each of said subsystem modems including:

a transmitting means for converting binary digital data received from said bidirectional forwarding means into FSK signal form such that a binary zero (0) causes said FSK signal to have said third frequency, F3, and a binary one (1) causes said FSK signal to have said fourth frequency, F4, and applying said F3 and F4 FSK signals to a related nonloaded loop;

receiving means for receiving said F1 and F2 FSK signals applied to said related nonloaded loop by said transmitting means of a related station modem and converting said F1 and F2 FSK signals into binary digital data form such that an F1 FSK signal causes a binary zero (0) and an F2 FSK signal causes a binary one (1) and applying said binary digital data to said bidirectional forwarding means; and

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a voice filter for connecting the other end of said nonloaded loop to said line switching equipment.

8. The improvement claimed in claim 7 wherein said transmitting means of the said subsystem modems includes a frequency synthesizer for producing said F3 and F4 FSK signals in accordance with the binary form digital data received from said bidirectional forwarding means and wherein said receiving means of said subsystem modems includes a frequency detector for detecting said F1 and F2 FSK signals and converting said F1 and F2 FSK signals into binary form digital data and applying said binary form digital data to said bidirectional forwarding means.

9. The improvement claimed in claim 8 wherein said bidirectional forwarding means comprises a multiplexer/demultiplexer for multiplexing the binary digital data produced by said receiving means of said subsystem modems and forwarding said multiplexed binary digital data to said data processing center and for receiving multiplexed binary digital data produced by said data processing center, demultiplexing said binary digital data produced by said data processing center and applying demultiplexed binary digital data to said transmitting means of said subsystem modems.

10. The improvement claimed in claim 7 wherein said bidirectional forwarding means comprises a multiplexer/demultiplexer for multiplexing the binary digital data produced by said receiving means of said subsystem modems and forwarding said multiplexed binary digital data to said data processing center and for receiving multiplexed binary digital data produced by said data processing center, demultiplexing said binary digital data produced by said data processing center and applying demultiplexed binary digital data to said transmitting means of said subsystem modems.

11. A data carrier system comprising:

(A) a plurality of pairs of nonloaded wires;

(B) a plurality of telephone stations, each of said telephone stations comprising;

(1) a telephone;

(2) a data terminal for producing and receiving digital data in binary form; and

(3) station modem means connected between said data terminal and said telephone, and one of said pairs of nonloaded wires for;

(a) converting digital data produced by said data terminal from binary form into FSK signal form such that a binary zero (0) causes said FSK signal to have a first frequency, F1, and a binary one (1) causes said FSK signal to have a second frequency, F2, and applying said F1 and F2 FSK signals to said one of said pairs of nonloaded wires; and

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(b) converting digital data carried by said pair of nonloaded wires from FSK signal form into binary signal form such that an FSK signal at a third frequency, F3, causes a binary zero (0) and an FSK signal at a fourth frequency, F4, causes a binary one (1) and applying said binary digital data to said data terminal;

(4) filtering means for connecting said telephone to said one of said pairs of nonloaded wires such that said telephone does not receive said F1, F2, F3 and F4 FSK signals;

(C) telephone switching equipment connected to the other end of said plurality of pairs of nonloaded wires, said telephone switching equipment including the switching equipment and a subsystem, said subsystem comprising;

(1) subsystem modem means connected to the other ends of said pairs of nonloaded wires for;

(a) converting said F1 and F2 digital data signals applied to said pairs of nonloaded wires by said station modem means from FSK signal form into binary form such that an FSK signal at said first frequency, F1, causes a binary zero (0) and an FSK signal at said second frequency, F2, causes a binary one (1); and

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(b) converting binary digital data produced by a bidirectional forwarding means from binary form into FSK signal form such that a binary zero (0) causes said FSK signal to have said third frequency, F3, and a binary one (1) causes said FSK signal to have said fourth frequency, F4, and applying said F3 and F4 FSK signals to predetermined ones of said pairs of nonloaded wires;

(2) filtering means for connecting said line switching equipment to said pairs of nonloaded wires such that said line switching equipment does not receive said F1, F2, F3 and F4 FSK signals; and

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(3) bidirectional forwarding means for;

(a) receiving binary digital data produced by said subsystem modem means, multiplexing said binary digital data and forwarding said binary digital data to a data processing center; and

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(b) receiving binary digital data produced by said data processing center and applying said data processing center digital data to said subsystem modem means; and

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(D) a data processing center for receiving and processing binary digital data signals produced by said subsystem modem means; and

, for producing binary digital data and forwarding said binary digital data to said bidirectional forwarding means of said subsystem.

12. The data carrier system claimed in claim 11 wherein said station modem means includes:

a transmitting means for converting binary digital data produced by said data terminal into FSK signal form such that a binary zero (0) causes said FSK signal to have said first frequency, F1, and a binary one (1) causes said FSK signal to have said second frequency, F2, and applying said F1 and F2 FSK signals to said pair of nonloaded wires; and

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receiving means for receiving said F3 and F4 FSK signals carried by said pair of nonloaded wires and converting said F3 and F4 FSK signals into binary digital data form such that an F3 FSK signal causes a binary zero (0) and an F4 FSK signal causes a binary one (1) and applying said binary digital data to said data terminal.

13. The data carrier system claimed in claim 12 wherein said transmitting means of the said station modem means includes a frequency synthesizer for producing said F1 and F2 FSK signals in accordance with the binary form digital data produced by said data terminal and wherein said receiving means of said station modems includes a frequency detector for detecting said F3 and F4 FSK signals and converting said F3 and F4 FSK signals into binary form digital data and applying said binary form digital data to said data terminal.

14. The data carrier system claimed in claim 13 including an automatic gain control circuit connected between said receiving means and said transmitting means of said station modems such that the amplitude of the F1 and F2 FSK signals produced by said frequency synthesizer of said transmitting means is controlled by the negative logarithm of the amplitude of the F3 and F4 FSK signals received by said receiving means.

15. The data carrier system claimed in claim 12 wherein said subsystem modem means includes a plurality of subsystem modems, each of said subsystem modems including:

a transmitting means for converting binary digital data received from said bidirectional forwarding means into FSK signal form such that a binary zero (0) causes said FSK signal to have said third frequency, F3, and a binary one (1) causes said FSK signal to have said fourth frequency, F4, and applying said F3 and F4 FSK signals to said pair of nonloaded wires; and

,

receiving means for receiving said F1 and F2 FSK signals applied to said pair of nonloaded wires by said transmitting means of said station modem means and converting said F1 and F2 FSK signals into binary digital data form such that an F1 FSK signal causes a binary zero (0) and an F2 FSK signal causes a binary one (1) and applying said binary digital data to said bidirectional forwarding means.

16. The data carrier system claimed in claim 15 wherein:

said transmitting means of the said station modem means includes a frequency synthesizer for producing said F1 and F2 FSK signals in accordance with the binary form digital data produced by said data terminal and said receiving means of said station modem means includes a frequency detector for detectng said F3 and F4 FSK signals and converting said F3 and F4 FSK signals into binary form digital data and applying said binary form digital data to said data terminal; and

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said transmitting means of the said subsystem modems includes a frequency synthesizer for producing said F3 and F4 FSK signals in accordance with the binary form digital data received from said bidirectional forwarding means and said receiving means of said subsystem modems includes a frequency detector for detecting said F1 and F2 FSK signals and converting said F1 and F2 FSK signals into binary form digital data and applying said binary form digital data to said bidirectional forwarding means.

17. The data carrier system claimed in claim 15 wherein said data processing center produces multiplexed binary digital data and wherein said bidirectional forwarding means comprises a multiplexer/demultiplexer for multiplexing the binary digital data produced by said receiving means of said subsystem modems and forwarding said multiplexed binary digital data to said data processing center and for receiving said multiplexed binary digital data produced by said data processing center, demultiplexing said binary digital data produced by said data processing center and applying demultiplexed binary digital data to said transmitting means of said subsystem modems.