Telephone set with circuit for suppression of howling and echo

Details Telephone set with circuit for suppression of howling and echo Telephone set with circuit for suppression of howling and echo

1995-12-07

1998-05-26

Chiang, Jack

Telephonic communications

Substation or terminal circuitry

Conversion of signal form

379389, 379395, 379390, H04M 100

Patent

active

057579059

ABSTRACT:
A telephone set has a receiver for transducing a reception signal into a voice, a microphone for transducing a voice into a transmission signal and a comparing device. The comparing device compares the reception signal and the transmission signal, and a predetermined frequency pass band is in turn alternated according to a period of a first clock input to pass the reception signal and the transmission signal. The comparing device outputs a frequency pass band where the reception signal and transmission signal have a substantially equal and maximum level and a comparison result signal when the reception signal and transmission signal have the substantially equal level. The telephone set also includes a frequency indicator which generates a second clock with a period corresponding to the frequency pass band value signal as well as supplying the first clock to the comparing device, and a transmission signal controller which transmits the transmission signal to a transmission line, and a frequency band to be eliminated from the transmission signal is variably set on the basis of the second clock.

REFERENCES:
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patent: 4491689 (1985-01-01), Boeckman
patent: 4571461 (1986-02-01), Uno et al.
patent: 4641339 (1987-02-01), Stottlemyer
patent: 4747132 (1988-05-01), Ibaraki et al.
patent: 4748663 (1988-05-01), Phillips et al.
patent: 4955055 (1990-09-01), Fujisaki et al.
patent: 4991167 (1991-02-01), Petri et al.
patent: 5271057 (1993-12-01), Addeo et al.
patent: 5526419 (1996-06-01), Allen et al.
patent: 5533120 (1996-07-01), Staudacher

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