Integrated circuit for telephone set with signal envelope detect

Details Integrated circuit for telephone set with signal envelope detect Integrated circuit for telephone set with signal envelope detect

1989-09-12

1991-01-01

Ng, Jin F.

Telephonic communications

Echo cancellation or suppression

379390, 379395, H04M 908

Patent

active

049824279

ABSTRACT:
The disclosure concerns digital telephone sets and, more particularly, those with amplified listening facility and "hands free" telephones. To fulfil the function of the anti-Larsen effect needed in these telephones, there is need for a signal envelope detector which gives a measurement of the mean level of the signal emitted or received on the line. According to the disclosure, the cofidec present in the digital telephones is used to establish an envelope detection system with logarithmic compression. This removes the need to do a logarithmic detection on the analog speech signal. Such a detection would necessitate diodes, upside down with respect to each other, which can be made, particularly, only through bipolar technology. A series/parallel converter, a digital comparator and a counter having a countdown frequency which is far slower than the counting frequency, fulfils the signal envelope detection function.

REFERENCES:
patent: 4513177 (1985-04-01), Nishino et al.
patent: 4555596 (1985-11-01), Blomley
patent: 4796287 (1989-01-01), Reesor et al.
NEC- Research and Development, No. 83, Oct. 1986, T. Makabe et al.
Motorola Technical Developments, vol. 5, No. 1, Oct. 1985, D. E. Bush.
Electronics, vol. 59, No. 33, Oct. 1986, R. Rosenberg.

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