Apparatus and method for determining the state of a telephone li

Details Apparatus and method for determining the state of a telephone li Apparatus and method for determining the state of a telephone li

1990-10-02

1992-08-18

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379379, H04M 322

Patent

active

051406314

ABSTRACT:
A line state detector for a telephone line tests a voltage derived from the telephone line by closing a switch in series with a voltage sensing circuit in response to a polling signal. A modem testing the line state go Off-Hook immediately after it finds that the line was in On-Hook state, so it can use a low impedance voltage sensor directly on the telephone line. Monitoring equipment will need a line state detector with high impedance, which can be achieved by a high impedance in series with a capacitor. The capacitor voltage can then be tested by a low impedance sensing circuit.

REFERENCES:
patent: 4220825 (1980-09-01), Fahey
patent: 4224478 (1980-09-01), Fahey et al.
patent: 4433212 (1984-02-01), Moses et al.
patent: 4679229 (1987-07-01), Yamaguchi
patent: 4845741 (1989-07-01), Fourdraine
patent: 4958371 (1990-09-01), Damoci et al.
patent: 4987586 (1991-01-01), Gross et al.
J. Cook et al., "General Electric Optoelectronics Manual", .COPYRGT.1976, pp. 70-72.

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