H - Electricity – 04 – M
Patent
H - Electricity
04
M
379/18, 379/33,
H04M 3/02 (2006.01) H04M 9/00 (2006.01) H04M 19/02 (2006.01) H04M 19/04 (2006.01)
Patent
CA 1038981
Abstract of the Disclosure A solid state interrupter is described for controlling the visual and audible indicators in telephone systems and more particularly to control the line selection lamps and electro-mechanical ringers in key telephone sets. The interrupter includes switching devices individually connected between a pair of lamp wink terminals, a pair of lamp flash terminals and a pair of ring signal terminals. Each of the switching devices includes a control circuit for alternately enabling and blocking the flow of current in the circuit between the associated terminals in response to the application of a predetermined control signal to the respective control circuit. An oscillator is provided for generating an a.c. reference signal. Suitable dividers and gates are connected between the oscillator and the control circuits of the switching devices to control the duty cycle and frequency that the circuit is closed between the associated terminals. The switching devices connected to the ring signal terminals includes an isolator for isolating the ringing signal terminals from the interrupter to eliminate ground current between the two circuits. The isolator may be in the form of a light sensitive transistor and a light emitting diode so that light emitted from the diode in response to current flow results in an impedance across the transistor.
238429
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