Telephone circuits

Details Telephone circuits Telephone circuits

1986-09-26

1989-01-03

Ng, Jin F.

Telephonic communications

Substation or terminal circuitry

Sidetone control or hybrid circuit

379395, 379398, H04M 158

Patent

active

047962950

ABSTRACT:
A circuit is disclosed for use in telephone handsets having a line signal node (1), a microphone signal input (20) and an output to an earphone amplifier. There is provided two voltage feedback loops via respective impedance networks (10, 11) and a current feedback loop (5, 7, 14). These feedback loops determine the impedance presented to the line at the signal node with specific voltage/current characteristics and signal frequencies. The first voltage feedback loop in conjunction with the current feedback loop defines the signal frequency impedance and the second voltage feedback loop defines the DC mask presented to the line.

REFERENCES:
patent: 3529099 (1970-09-01), Ribner
patent: 4358644 (1982-11-01), Hubler
patent: 4515996 (1985-05-01), Burgin
patent: 4536616 (1985-08-01), Kaire
"A Programmable Speech Circuit Suitable for Telephone Transducers", P. Consiglio et al., IEEE Journal of Solid-State Circuits, vol. SC-17, No. 6, Dec. 1982, pp. 1149-1157.
"Phone IC Banishes Carbon Mike, Takes on Hybrid Coil's Functions", S. D'Arrigo et al., Electronics, Jun. 16, 1982, pp. 153-155.

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