Telephone line interface circuit with voltage switching

Details Telephone line interface circuit with voltage switching Telephone line interface circuit with voltage switching

1992-04-02

1994-06-21

Dwyer, James L.

Telephonic communications

Subscriber line or transmission line interface

379340, 379400, 379413, 379324, H04M 1900

Patent

active

053234618

ABSTRACT:
A two-wire telephone line interface circuit comprises a driver circuit for supplying direct current on the line, a controlled voltage generator, a sensing circuit for monitoring the line current, a control circuit for controlling an output voltage of the voltage generator, and a switching circuit. The control circuit controls the switching circuit to supply, as a supply voltage for the driver circuit, a battery voltage in an on-hook state of the line or the controlled output voltage of the voltage generator in an off-hook state of the line, this output voltage being controlled to provide off-hook current limiting. The control circuit also controls the switching circuit to selectively supply the controlled output voltage of the voltage generator as a signalling voltage to at least one wire of the line for high voltage signalling, e.g. ringing, on the line. Desirable forms of the switching circuit are described.

REFERENCES:
patent: 4161633 (1979-07-01), Treiber
patent: 4315106 (1982-02-01), Chea, Jr.
patent: 4317963 (1982-03-01), Chea, Jr.
patent: 4355209 (1982-10-01), Sabon
patent: 4410766 (1983-10-01), Beirne
patent: 4419542 (1983-12-01), Embree et al.
patent: 4431868 (1984-02-01), Bolus et al.
patent: 4431869 (1984-02-01), Sweet
patent: 4764956 (1988-08-01), Rosch et al.
"Service Adaptive Access" by Q. Chow and G. Mein, Telesis 1990 one/two, Jul. 1990, pp. 54-56.

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