Telephone in use indicator (line busy lamp)

Abstract

Abstract An opto-electronic device, which by the electrical connection to both legs of a line, will indicate whether an extension telephone set on the same line is in use. The device consumes negligible line current both in lit mode and unlit mode, requires no additional power source nor any modifications to be made to installation nor to the circuit of any telephone or similar Telecom equipment into which it will be fitted. The light output can be constant or by inclusion of a flasher circuit made to pulsate. The device functions by using a voltage dependant switch Q1, Q2 to turn the LED on when the line voltage drops due to the line being loaded (used), regardless of where on that line it is being used or however many other line status indicators are fitted into other extensions, phones with or without this device fitted can be freely mixed on each line. <IMAGE>

Inventors

• 👤 Peter Henderson

Bibliographic Details