Voice control circuit for a communication terminal

Details Voice control circuit for a communication terminal Voice control circuit for a communication terminal

1988-05-16

1990-01-02

Ng, Jin F.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379388, 381106, H04M 160

Patent

active

048918377

ABSTRACT:
A voice control circuit controls the volume range of the voice signals in a communication terminal, such as a video telephone having a hands-free facility. In a hands-free facility, the signal-to-noise ratio is lower than in telephones with handset. To avoid audible feedback, hands-free facility conventionally includes a volume control circuit which decreases or increases the gain in the receive path as the gain in the set path increases or decreases. The problem to be solved is to utilize the maximum possible loop gain without reducing the gain in the receive path. The idea is to place behind the microphone (50) a controllable compandor (52) in which the signal voltages from the microphone (50) are A. compressed if they lie above a predetermined level, B. expanded if they lie below the predetermined level, and C. imparted maximum gain if they have the predetermined level. The predetermined signal level, which corresponds to the compression set point, is varied by a control circuit (90) as a function of the ambient noise.

REFERENCES:
patent: 4240037 (1980-12-01), Rubin
patent: 4543665 (1985-09-01), Sotelo et al.
patent: 4550426 (1985-10-01), Gillig et al.
patent: 4677678 (1987-06-01), McCutchen
patent: 4696032 (1987-09-01), Levy
patent: 4718099 (1988-01-01), Hotvet
Patent Abstracts of Japan, Band 9, Nr. 106 (E-313)[1829], 10 May 1985; & JP-A-59 230 356 (Matsushita Denki Sangyo K.K.) 24 Dec. 1984.
"Die neue sprachgesteuerte Freisprechneinrichtung fur die Produktfamilie INTERMAT", V. M. Slawik et al., Elektrisches Nachrichtenwesen, Band 53, No. 4, 1978.
"Voice Controlled Handsfree Subset for the Intermat Range", M. Slawik, Electrical Comm., vol. 53, No. 4, 1978.

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