Speaking apparatus having handfree conversation function

Details Speaking apparatus having handfree conversation function Speaking apparatus having handfree conversation function

1994-05-16

1995-12-26

Hofsass, Jeffery A.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379406, 379410, 379411, 379388, H04M 908

Patent

active

054795028

ABSTRACT:
A speaking apparatus having a handfree conversation function, provided with an echo canceler which can cancel the echo caused by direct acoustic coupling between a speaker and a microphone positioned in a system having a casing, a ground surface and a speech switching circuit. In the apparatus, the amount of insertion attenuation of the transmitted and received signal is set with an upper limit of the amount of attenuation sufficient for cancelling the echo caused by the indirect acoustic coupling determined by the location where the speaking apparatus is used. In addition, the echo canceler and the speech switching circuit share optimum functions to obtain an excellent speaking quality apparatus with an inexpensive and small sized processing circuit.

REFERENCES:
patent: 4636586 (1987-01-01), Schiff
patent: 4912758 (1990-03-01), Arbel
patent: 4947425 (1990-08-01), Grizmala et al.
Hsu et al., "Acoustic Echo Cancellation for Loudspeaker Telephones", IEEE/IEICE-Global Telecommunications Conference, vol. 3/3, Nov. 1987, pp. 1955-1959, XP94127.
Proceedings of Eusipco-88 Fourth European Signal Processing Conference, "High Quality Hands-Free Telephony Using Voice Switching Optimized with Echo Cancellation", pp. 495-498, Sep., vol. 11, 1988.
Proceedings of Eusipco-88 Fourth European Signal Processing Conference, "Achieving the Control of the Acoustic Echo in Audio Terminals", pp. 491-494, Sep., vol. 11, 1988.

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