Hands-free telephone set

Details Hands-free telephone set Hands-free telephone set

1993-09-15

1995-01-24

Dwyer, James L.

Telephonic communications

Substation or terminal circuitry

Sidetone control or hybrid circuit

379390, 379389, 379388, 381113, 381 92, H04M 908

Patent

active

053848438

ABSTRACT:
An acoustic echo canceler and a side-tone echo canceler provided in a hands-free telephone suppress an acoustic echo and a side-tone echo respectively with few error by providing automatic gain controllers and/or limiters in the hands-free telephone so that the acoustic echo canceler and the side-tone echo canceler operate in linear, and a directional characteristic of a microphone used in the hands-free telephone for reducing the acoustic echo is controlled by a microphone direction controller so that the microphone operates as an omnidirectional microphone when a level of a received signal of the hands-free telephone is less than a designated level and as a bidirectional microphone when the level exceeds the designated level, further gains of an output of the microphone increases in a low frequency range.

REFERENCES:
patent: 4414433 (1983-11-01), Horie et al.
patent: 4703506 (1987-10-01), Sakamoto et al.
patent: 5027393 (1991-06-01), Yamamura et al.
patent: 5075687 (1991-12-01), Chen et al.

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