Importance

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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.

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First Claim