Reference signal circuit in a receiver for detecting two frequen

Details Reference signal circuit in a receiver for detecting two frequen Reference signal circuit in a receiver for detecting two frequen

1976-12-30

1978-04-04

Claffy, Kathleen H.

H04M 150

Patent

active

040829243

ABSTRACT:
A reference signal circuit in a multi-frequency signal receiver for detecting the two signalling frequencies in an incoming voice frequency signal. The circuit has two paths for receiving the incoming signal. One path includes a rectifier and attenuation device to give a first signal level dependent on the incoming signal level. The other path includes a first comparator to compare the instantaneous level of the incoming signal with such first signal level, a timing circuit and a second comparator in order to obtain a second signal level whose amplitude is dependent on the duration of the incoming signal. The outputs of the two signal paths are interconnected via a gating circuit to feed a reference voltage to analog signal comparators included in the multi-frequency signal receiver.

REFERENCES:
patent: 3875347 (1975-04-01), Alaily
patent: 3934096 (1976-01-01), Kusano

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