Telephone subscriber circuit with galvanic isolation

Details Telephone subscriber circuit with galvanic isolation Telephone subscriber circuit with galvanic isolation

1994-10-27

1997-11-25

Zele, Krista M.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379399, 379413, 379414, H04M 100

Patent

active

056920415

ABSTRACT:
A telephone subscriber circuit is coupled via a single galvanic isolation element to provide, from a subscriber apparatus unconnected to the telephone line, on- and off-hook signals to the telephone line and to control transfer of telephonic signals between the subscriber apparatus and the telephone line. The galvanic isolation element is a photocoupler. The subscriber circuit includes a speech circuit coupled to the line through a diode bridge circuit and an electronic switch is connected between the speech circuit and the diode bridge circuit. An input terminal of the speech circuit and a control terminal of the electronic switch are each connected through a voltage-generating circuit and level-translating circuit to an output terminal of the galvanic isolation element.

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patent: 5432835 (1995-07-01), Hashimoto
Hafer, R., "Designing Telephone-Interface Circuitry With Solid-State Relays," Electronic Design International 38(23): 91-93, 95-96, 1990.

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