Tone activated hold circuit

Details Tone activated hold circuit Tone activated hold circuit

1982-05-20

1983-12-06

Pellinen, A. D.

179 99H, 179 84VF, H04M 100

Patent

active

044195435

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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patent: 4219701 (1980-08-01), Feiner
patent: 4223183 (1980-09-01), Peters, Jr.
patent: 4243844 (1981-01-01), Waldman
patent: 4365117 (1982-12-01), Curtis

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