Key telephone call signalling circuit
Number of patents in Portfolio can not be more than 2000
United States of America Patent
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-
Jan 22, 1980
Issued Date -
N/A
app pub date -
Jul 18, 1978
filing date -
Oct 1, 1976
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
The disclosure is directed to a calling circuit which controls the connection of two different audio signal sources to a single audio signal transmission path for broadcasting the audio signals over a telephone set loudpseaker as well as controlling the energization of indicators in the telephone set and at the main control circuit. Only four conductors are used to connect the telephone set with the main control circuit, two of which are power supply conductors which may supply other circuits as well.
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