Telephone line visual status indication circuit

Details Telephone line visual status indication circuit Telephone line visual status indication circuit

1974-11-07

1976-04-20

Claffy, Kathleen H.

179175, H04M 322

Patent

active

039512487

ABSTRACT:
In telephone installations it is often necessary to know, without actually physically going off-hook, the status of the line. A solution to this problem is presented by the design of a low drain line status indicator circuit. Advantage is taken of the fact that the idle line voltage available from the switching machine is significantly greater than the busy line voltage. Accordingly, when the line is idle, a pulsating voltage is developed which is used to flash a light source at the station. When the line is busy or on hold, which situation can occur from a telephone station set connected to a remote extension, the line voltage is insufficient to enable the pulsating voltage circuit and, thus, the light source remains dark. In situations where one telephone station set serves two lines, the light sources associated with each line at each station location are arranged to flash in synchronism.

REFERENCES:
patent: 3374317 (1968-03-01), Chapin
patent: 3729597 (1973-04-01), Garrett
patent: 3801974 (1974-04-01), Aitken

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