Digital loudspeaking telephone

Details Digital loudspeaking telephone Digital loudspeaking telephone

1985-09-27

1989-01-03

Ng, Jin F.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379388, H04M 160

Patent

active

047962879

ABSTRACT:
A digital loudspeaking telephone for connection to a telephone line, including a microphone, speaker, codec and digital signal processor. Incoming and outgoing signals are received by the digital signal processor from remote and local subscribers via the telephone line and microphone respectively. The processor generates and compares incoming and outgoing envelope and noise floor signal levels derived from the received incoming and outgoing signals and in response suppresses a particular compared, and one of the incoming or outgoing signals. Automatic gain control of outgoing signals is implemented in order to allow smooth switching of the outgoing signals and to suppress background noise from being transmitted by the microphone. Room echo and reverberation are also detected, and the processor eliminates spurious channel switching due to the detected echo signals.

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