Device for forming the hands-free function in a telephone set, a

Details Device for forming the hands-free function in a telephone set, a Device for forming the hands-free function in a telephone set, a

1989-11-03

1991-01-08

Dwyer, James L.

Telephonic communications

Substation or terminal circuitry

For loudspeaking terminal

379387, H04M 908, H04M 340

Patent

active

049842650

ABSTRACT:
Device for performing the "hands-free" function in a telephone set associating the gain switching and echo cancellation functions. This device is characterized in that it comprises a gain switch and an echo canceller, said switch having in the emission and reception channels a circuit for measuring the amplitude of the signals present on these channels, a checking circuit for determining the state of the telephone set (emission, reception, rest,) a calculating member controlled by the checking circuit, variable attenuators controlled by the calculating member, said calculating member evaluating, as a function of the relative amplitudes of the signals in emission and in reception, the echo cancellation performances obtained by the device and adjusting as a function thereof the variable attenuators in each channel, so that the overall attenuation in the loop always assumes the minimum value ensuring the stability of the system.

REFERENCES:
patent: 3499999 (1970-03-01), Sondhi
patent: 3588385 (1971-06-01), Moye
patent: 4560840 (1985-12-01), Hansen
patent: 4629829 (1986-12-01), Puhl et al.
patent: 4712235 (1987-12-01), Jones, Jr.
patent: 4747132 (1988-05-01), Ibaraki et al.
Patent Abstracts of Japan, vol. 9, No. 169 (E-328), 1982, 13.7.1985, JP-A-60 41 849 (Toshiba K.K.) 5.3.1985.
Patent Abstracts of Japan, vol. 7, No.123, (E-178), 1268, 27.5.1983, JP-A-58 42 345.

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