Digital data transmission system
US4302629A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 1, 1979 |
| Grant date | Nov 24, 1981 |
| Priority date | — |
| Expiry date | Aug 1, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L27/122
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
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 subsyste…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.