Speech communication apparatus

Details Speech communication apparatus Speech communication apparatus

1994-01-28

1997-12-09

Zele, Krista M.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379388, 379406, 379410, 379409, 370286, 370289, H04M 908

Patent

active

056968191

ABSTRACT:
A dual mode mobile telephone apparatus includes an echo canceler. In a hands-free conversation mode, a received speech output from a loudspeaker is input to a microphone by circulate cross talk and transmitted to the destination side so that an acoustic echo may be generated. The echo canceler cancels the acoustic echo. A center clipper for eliminating a residual echo signal having a level lower than a preset level is provided at the output side of the echo canceler. Enabling/disabling operations of the center clipper are controlled in accordance with a volume control level for a reception signal and transmission/reception state detection signal from a voice switching circuit which controls gains of reception channel and transmission channel in the opposite directions.

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