Microphone circuit

Details Microphone circuit Microphone circuit

1987-12-14

1990-05-01

Eisenzopf, Reinhard J.

Telecommunications

Transmitter and receiver at same station

With transmitter-receiver switching or interaction prevention

455 80, 381168, H04B 146

Patent

active

049225472

ABSTRACT:
A microphone circuit for a mobile telephone is capable of operations in either of two modes, i.e. in a hands-free or a push-to-talk mode. A constant current circuit is coupled in parallel with the microphone to preclude a change in a DC bias voltage responsive to switch operations, especially in a push-to-talk mode. A voltage comparator compares the bias voltage with a reference to detect control signals and selects a preferred mode of operation.

REFERENCES:
patent: 3191066 (1962-10-01), Staudenmayer
patent: 4087636 (1978-05-01), Akiyama et al.
patent: 4246582 (1981-01-01), Kondo et al.
patent: 4400581 (1983-08-01), Jacobson
patent: 4400584 (1983-08-01), Vilmur
patent: 4457018 (1984-06-01), Takayama
patent: 4549309 (1985-10-01), Corrigan
patent: 4682350 (1987-07-01), Akerberg
patent: 4720856 (1988-01-01), Pace et al.

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