Multiplex communications – Wide area network – Packet switching
Patent
1985-01-15
1987-11-10
Griffin, Robert L.
Multiplex communications
Wide area network
Packet switching
370 71, 370 74, 379160, 379202, 379206, H04J 102
Patent
active
047062444
ABSTRACT:
A frequency multiplexed system for coupling a plurality of individual telephone sets to at least one subscriber telephone line. The system includes a line adapter unit for controlling use of subscriber lines and for assigning the use of frequency bands to the individual telephone sets. The system includes a two-conductor interconnection cable for coupling to each of the telephone sets and to the line adapter unit. The system has a power-down mode in which the loss of external power allows each of the individual telephone sets to use the subscriber line. The line adapter unit and each of the individual telephone sets employ transconductance amplifiers so that modulated current signals are produced on the interconnection cable, thus allowing a plurality of voice signals to be summed together by voltage addition for conferencing between the telephone sets and the subscriber lines. One embodiment of the invention includes the production of a pilot reference signal on the interconnection cable by the adapter unit so that synchronous modulation and demodulation by each of the telephone sets is made possible.
REFERENCES:
patent: 3202765 (1965-08-01), Byrne
patent: 3864521 (1975-02-01), DeLong et al.
patent: 3931477 (1976-01-01), Warman
patent: 4020288 (1977-04-01), Bellanger et al.
patent: 4087639 (1978-05-01), Beene et al.
patent: 4503289 (1985-03-01), Spires
Avella Frank
Co Ramon S.
Fuhrman James L.
Watson George A.
Arthur David J.
Griffin Robert L.
Hamann H. Fredrick
Montanye George A.
Rockwell International Corporation
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