Two-wire telecommunications line detection arrangements

Details Two-wire telecommunications line detection arrangements Two-wire telecommunications line detection arrangements

1993-03-03

1995-08-29

Dwyer, James L.

Telephonic communications

Supervisory or control line signaling

Using line or loop condition detection

379252, 379164, H04M 322

Patent

active

054467861

ABSTRACT:
A hook state detector for a two-wire telephone line includes two comparators each for comparing a voltage on a respective wire of the line with a respective reference voltage, and a logic circuit or software responsive to outputs of the comparators for determining off-hook and on-hook states when one of the compared voltages is more negative and the other is more positive than the respective reference voltages, and maintaining a previous hook state determination when both of the compared voltages are more positive, and when both of the compared voltages are more negative, than the respective reference voltages. The arrangement is insensitive to common mode induced a.c. on the line. The comparators can comprise differential amplifiers or opto-couplers.

REFERENCES:
patent: 4110569 (1978-08-01), Schindler et al.
patent: 4429185 (1984-01-01), Adrian
patent: 4456791 (1984-06-01), Forestier
patent: 4622439 (1986-11-01), Kasbia et al.
patent: 4802207 (1989-01-01), Uchida
patent: 4935959 (1990-06-01), Markovic et al.

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