Subscriber circuit with built-in polarity switching circuit

Details Subscriber circuit with built-in polarity switching circuit Subscriber circuit with built-in polarity switching circuit

1997-08-13

1999-08-24

Eisenzopf, Reinhard J.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379399, H04M 100

Patent

active

059434198

ABSTRACT:
The subscriber circuit has a balanced amplifier and a built-in call-current polarity changing circuit. Moreover, the output stage circuits of the direct feed-back and offset cancel circuits of the subscriber circuit have the same configuration. By switching the input voltage supplied to the direct feed-back and offset cancel circuits by a switch, the signals fed back to the inputs of the balanced amplifier are switched. Thus, the polarity of the loop current can be inverted. Furthermore, it is possible to switch the loop current without adopting an extra circuit, and the part of the circuit in which the switches are not required to withstand pressure can be constructed with CMOS thereby allowing minimization of the circuit size.

REFERENCES:
patent: 4430621 (1984-02-01), Weiser et al.
patent: 4760595 (1988-07-01), Arai
patent: 5124663 (1992-06-01), McEntarfer et al.
patent: 5329588 (1994-07-01), Willocx et al.
patent: 5446405 (1995-08-01), Ikeda
patent: 5511118 (1996-04-01), Gores et al.

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