Handsfree telephone

Details Handsfree telephone Handsfree telephone

1984-03-14

1986-01-14

Olms, Douglas W.

Multiplex communications

Wide area network

Packet switching

179 81B, H04J 302

Patent

active

045649391

ABSTRACT:
In a handsfree telephone system of the type described in our application No. 584,579, filed in the U.S. on Feb. 29, 1984, the method used to avoid howling due to feedback from the loudspeaker to the microphone is to increase the attenuation to speech in the quiescent direction as compared with that in the active direction. This involves monitoring successive speech samples in the two directions with each sample compared with a preset threshold, which also takes account of the system's noise levels. This is effected under processor control, as in the adjustment of the attenuation, since the system uses digital speech transmission.
It has now been found that it is not necessary to monitor all speech samples to derive adequate information about the occupancy conditions of the two speech directions. In the present systems only one speech sample in four is used. This enables one microprocessor to serve two lines alternately. Although this increases the amount of measuring used this costs less than the microprocessor which has been saved.

REFERENCES:
patent: 3976847 (1976-08-01), Bidlack et al.
patent: 4063047 (1977-12-01), Huryn
patent: 4161624 (1979-07-01), Brosow
patent: 4276639 (1981-06-01), Fukuda et al.
patent: 4459434 (1984-07-01), Benning et al.

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