System and method for performing telephone line-in-use detection

Details System and method for performing telephone line-in-use detection System and method for performing telephone line-in-use detection

1998-06-11

2000-08-15

Chan, Wing F.

Telephonic communications

Telephone line or system combined with diverse electrical...

Having transmission of a digital message signal over a...

379 9309, H04M 1100

Patent

active

061047910

ABSTRACT:
A device connectable to a telephone line including detection circuitry for detecting telephone line events, such as telephone line-in-use, extension pick-up, and remote hang-up. The telephone line events are detected by monitoring the line voltage and loop current transmitted through the telephone line from a central office. A voltage sensor is connected to the telephone line to detect changes in the line voltage appearing in the telephone line. The changes detected in the line voltage are used in a line-in-use detection circuit to determine if the telephone line is already being used by another extension, while changes in loop current are used in a remote hang-up detection circuit to determine when a remote party ends their connection with the telephone line. An extension pick-up circuit is further provided for sensing changes in the telephone loop current in order to determine if a telephone extension has been picked up. If any of the circuits sense that one of these telephone conditions has occurred, the device may then change its mode of operation.

REFERENCES:
patent: 5422939 (1995-06-01), Kramer, et al.
patent: 5506891 (1996-04-01), Brown
patent: 5535265 (1996-07-01), Suwandhaputra

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