Speech circuit for subscriber telephone apparatus

Details Speech circuit for subscriber telephone apparatus Speech circuit for subscriber telephone apparatus

1996-04-10

1998-01-20

Bost, Dwayne

Telephonic communications

Substation or terminal circuitry

Impedance matching or line equalizing

379394, 379391, 379392, H04M 100

Patent

active

057108110

ABSTRACT:
The speech circuit matches the impedance of the telephone line by synthesizing a complex impedance using a positive feedback loop which has a single resistor (11), and cancels out the side tone using a subtractor (20') which extracts from the signal (Va) coming from the line a signal (Vb) correlated to the signal to be transmitted. In order to achieve cancellation of the side tone unaffected by the noise produced in the impedance synthesizing circuits, the signal (Vb) is derived by processing the signal present in the resistor (11) at the output of the feedback loop.

REFERENCES:
Castello, et al., "A BiCMOS Speech Circuit With Only Two External Components," IEEE Journal of Solid-State Circuits, vol. 28, No. 7, Jul. 1993, NY, pp. 770-777.

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