Full duplex speakerphone

Details Full duplex speakerphone Full duplex speakerphone

1989-04-10

1990-10-23

Dwyer, James L.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379411, H04M 160, H04M 908

Patent

active

049658220

ABSTRACT:
Disclosed is an adaptive Finite Impulse Response ("FIR") filter speakerphone that provides improved echo cancelation by the inclusion of a tracking comb filter having nulls which change to track the voice portion of communications. The speakerphone also includes a pair of ambient noise recorders for recording both ambient background noise received from the telephone line and ambient background noise in the signal to be transmitted to the telephone line. During intervals of low signal level, pre-recorded ambient noise is substituted for the communication signals. The speakerphone also controls the respective strengths of the received and transmitted signals during intervals when voice signals are present. A delay buffer adapts the speakerphone for use in videoconferencing.

REFERENCES:
patent: 4629829 (1986-12-01), Puhl et al.
patent: 4670903 (1987-06-01), Araseki et al.

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