Matsushita Electric Industrial Co., Ltd.

Kazuyoshi Fujiyoshi

Kyoji Murakami

An antisidetalk signal control circuit for preventing transmission of signals from a first source connected with a first input circuit to an output circuit while allowing the transmission of signals from a second source connected with a second input circuit to the output circuit. The signal control circuit comprises a first switching circuit having an input coupled to the first input circuit, a second switching circuit having an input coupled to the first output circuit through a phase inverter and a third switching circuit having an input coupled to the outputs of the first and second switching circuits. An oscillator drives the first switching circuit with signals having a given phase and the second and third switching circuits with signals of opposite phase. A low-pass filter couples the junction of the first and second switching circuits to the second input circuit and a feedback circuit couples the second input circuit to the junction of the first and second switching circuits. The reduction in sidetalk is not affected by variations in the impedances of the first and second signal sources.

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Fukuoka, Japan

Kazuyoshi Fujiyoshi