Telegraphy – Systems – Printing
Patent
1974-06-11
1976-02-17
Olms, Douglas W.
Telegraphy
Systems
Printing
179 15BS, 178 695DC, H04N 504
Patent
active
039393062
ABSTRACT:
A central office of a videotelephone system has a cross-bar switch to establish connections between incoming and outgoing video lines terminating at the transmitters and receivers of the videotelephone sets of the several outlying stations. A central sync-pulse generator works into the incoming video lines to control the sweep circuits of the video receivers of stations to which connections have been established, each video receiver being linked with the associated video transmitter through a delay circuit which actuates the line-scan generators of the transmitter and of the receiver with a relative offset compensating for the transit time of the sync pulses between the central office and the station. The sync pulses are supplied to each incoming video line through an amplifier stage preceded by a shunt circuit including a transistor to which quenching pulses for grounding the line are periodically applied by the sync-pulse generator.
REFERENCES:
patent: 3525808 (1970-08-01), Brown
patent: 3567861 (1968-12-01), Webb
Dubno Herbert
Olms Douglas W.
Ross Karl F.
Societa Italiana Telecomunicazioni Siemens S.p.A.
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