Telephonic communications – Substation or terminal circuitry – Sidetone control or hybrid circuit
Patent
1993-07-16
1995-03-07
Dwyer, James L.
Telephonic communications
Substation or terminal circuitry
Sidetone control or hybrid circuit
379390, 379392, H04M 158, H04M 162
Patent
active
053965493
ABSTRACT:
A telephone set includes an anti-sidetone circuit formed by a feedback loop having a filter in the feedback path. The feedback loop output is substantially equal to the signal produced at the set connection terminals by the microphone. Preferably the filter is composed of two sub-filters connected in cascade, formed of switched capacitors in an integrated circuit. An EEPROM control circuit can be included to permit easy programming during manufacture, to match a selected transmission line impedance.
REFERENCES:
patent: 3789155 (1974-01-01), Fensom
patent: 4791638 (1988-12-01), Fujie
patent: 4796295 (1989-01-01), Gay et al.
patent: 4983975 (1991-01-01), Sugino et al.
patent: 5029203 (1991-07-01), Ikefuji et al.
patent: 5191606 (1993-03-01), Juang
"Analog MOS Integrated Circuits for Signal Processing" R. Gregorian et al., Wiley 1986, pp. 1-25, 265-277, 280-284.
"Switched current filters", J. B. Hughes et al, IEE Proceedings, vol. 137, Pt. G. No. 2, Apr. 1990, pp. 156-162.
Philips Data Handbook "ICs for Telecom Subscriber Sets, Cordless Telephones, Mobile/Cellular Radio Pagers CA 3089 to PC 4413", Data Handbooks ICO3a and ICO3b, 1991.
Philips Data Handbook "ICs for Telecom Subsrciver Sets, Cordless Telephones, Mobile/Cellular Radio Pagers", PCD4413A to 74HC/HCT7046A.
Becker Rolf F. P.
Mulder Jacob
Wang Zhenhua
Dwyer James L.
Treacy David R.
U.S. Philips Corporation
Weaver Scott L.
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