Line use indicator for telephone sets sharing a single line

Details Line use indicator for telephone sets sharing a single line Line use indicator for telephone sets sharing a single line

H - Electricity

04

M

379/83

H04M 1/72 (2006.01)

Patent

CA 1201542

LINE USE INDICATOR FOR TELEPHONE SETS SHARING A SINGLE LINE Abstract of the Disclosure Where several telephone sets are connected to a single telephone line, it would be convenient to have a visual indication that the line is in use, to avoid lifting a handset to see if there is a conversation, for example. A circuit is installed across the telephone line, the circuit having a voltage divider connected between Tip and Ring, a first transistor with its base connected to the center of the voltage divider, a second transistor with its base connected to the collector of the first transistor and a third transistor having its base connected to the emitter of the second transistor, with a light emitting device connected between either Tip or Ring conductor and the collectors of the second and third transistors. The light emitting device can be a light emitting diode. An optical coupler cooperative with the light emitting device can be used to turn on power to light emitting devices in all the telephones, from a separate power source. - 1 -

443516

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