Telephone line interface circuit

Details Telephone line interface circuit Telephone line interface circuit

1990-05-09

1992-04-14

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379387, 379359, 379362, H04M 100

Patent

active

051054612

ABSTRACT:
A telephone line interface circuit for connecting telephone equipment provided with internal speech lines having predetermined DC impedance to external telephone lines, comprising a rectifying circuit connected with the telephone lines for rectifying the DC voltage coming from the telephone lines; a dial pulse sending circuit which makes connection and disconnection between the output terminals of the rectifying circuit and the internal speech lines for sending dial pulses to the telephone lines; and a polarity inversion detecting circuit which discriminates th evoltage relationship between the telephone lines and the internal speech lines for detecting the polarity inversion of the DC voltage coming from the telephone lines.

REFERENCES:
patent: 4306119 (1981-12-01), Kutzavitch
patent: 4527016 (1985-07-01), Sublette
patent: 4736412 (1988-04-01), Schmidt
patent: 4737986 (1988-04-01), Tsunoda
patent: 4815126 (1989-03-01), Goode et al.
patent: 4887295 (1989-12-01), Jenkins
patent: 4935959 (1990-06-01), Markovic et al.

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