Telephone line interface circuit

Details Telephone line interface circuit Telephone line interface circuit

1989-02-24

1990-03-20

Dwyer, James L.

Telephonic communications

Subscriber line or transmission line interface

379344, 379398, 340425, H04M 704

Patent

active

049107690

ABSTRACT:
The invention relates to a telephone line interface circuit for use in switching a call connection between subscriber telephone sets via a switching matrix. The interface circuit is provided with two terminals for connection to a telephone line of a subscriber and two terminals for connection to one side of a switching matrix. The circuit comprises a cascade circuit of a first and a second bidirectional amplifier which are connected to each other via a common point, acting as a one-to-N transformer for speech signals. Also included is a third and fourth bidirectional amplifier for providing direct voltage decoupling and impedance to thereby provide the telephone set with the required line voltage.

REFERENCES:
patent: 2659774 (1953-11-01), Barney
patent: 4540852 (1985-09-01), Albouy et al.
IBM Technical Disclosure Bulletin, "Subscriber Telephone Line Circuit", vol. 8, No. 5, Oct. 1965, p. 727.
21st Electronic Components Conference, "Integrated Circuit Transformers", J. J. Golembeski, Zie Voor Titel Boek; de 2 Pagina, pp. 359-364.
Patent Abstract of Japan, "Hybrid Circuit of Circular Type", Nippon Hoso Kyokai, vol. 1, No. 32, 29, maart 1977.

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