Tone activated hold circuit
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United States of America Patent
Stats
-
Dec 6, 1983
Grant Date -
N/A
app pub date -
May 20, 1982
filing date -
May 20, 1982
priority date (Note) -
Expired
status (Latency Note)
Importance
Abstract
A hold circuit for use with Dual Tone Multi Frequency telephone systems including a bistable circuit connected across the telephone line, the ON state drawing sufficient current from the telephone line to hold the circuit and the OFF state being substantially infinite impedance, a tone detection circuit which triggers the bistable circuit ON when the two frequencies produced by the '*' button are sensed, and a means for triggering the bistable circuit OFF responsive to the drop in line voltage due to a telephone on the line being taken off-hook.
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Cited Art Landscape
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