Voice circuit of telephone

Details Voice circuit of telephone Voice circuit of telephone

1986-08-20

1988-02-02

Brown, Thomas W.

Telephonic communications

Substation or terminal circuitry

Impedance matching or line equalizing

379395, H04M 176, H04M 160

Patent

active

047232781

ABSTRACT:
A voice circuit of a telephone is provided with a differential amplifier and an impedance setting circuit. An output of an amplifier to amplify an output signal of a transmitter is supplied to the inverting input terminal of the differential amplifier. An output of the impedance setting circuit is supplied to the noninverting input terminal of the differential amplifier. An output signal of the differential amplifier is supplied to a line driver. A positive feedback loop is constituted by the differential amplifier, line driver, telephone line, and impedance setting circuit. By controlling a feedback amount in this positive feedback loop, an AC impedance is controlled.

REFERENCES:
patent: 3742152 (1973-06-01), Matsuda et al.
patent: 3789155 (1974-01-01), Fensom
patent: 4071713 (1978-01-01), Sencer
patent: 4394542 (1983-07-01), Hara et al.
patent: 4680789 (1987-07-01), Sijbers et al.
Horowitz and Hill, The Art of Electronics, Sec 2.04-Emitter Followers as Voltage Regulators, p. 56.

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