Telephone line seizure circuit

Details Telephone line seizure circuit Telephone line seizure circuit

1997-12-31

2000-06-27

Loomis, Paul

Pulse or digital communications

Repeaters

Testing

379 40, 379 51, 379195, H04M 124, H04M 308, H04M 322, H04M 1104

Patent

active

060815469

ABSTRACT:
A telephone system including circuitry for monitoring the "on hook" and "off hook" conditions of telephone handsets coupled to a system controller and disconnecting all off hook handsets from the telephone line. With the detection of an alarm condition at a security alarm system that requires a communication link, line seizure is effected via an SCR controlled seizure circuit serially connected between each distributed handset and the telephone line. The seizure circuit normally conducts when a connected telephone is off hook. Upon detecting an alarm, a line monitor momentarily shorts the telephone line to drive any conducting line seizure circuits into a non-conducting condition that is maintained sufficiently long to permit the system controller to gain control of the line. During controller communications, the handsets are also isolated from the telephone line. A local phone is also coupled to permit reprogramming if an inoperative line is detected. A speech interface facilitates system programming via a central station.

REFERENCES:
patent: 4390750 (1983-06-01), Bartelink
patent: 5465297 (1995-11-01), Azem
patent: 5799062 (1998-08-01), Lazzara et al.
patent: 5877683 (1999-03-01), Sheasley

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