Title: Interrupter for telephone systems

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Abstract: 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 electromechanical ringers in key telephone sets. The interrupter includes switching means 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 means 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 control circuit thereof. 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 means to control the duty cycle and frequency at which a circuit path is made between the associated terminals. The switching means connected to the ring signal terminals includes means for isolating the ringing signal terminals from the interrupter to eliminate ground current between the two circuits. The isolator means 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 therethrough results in an impedance change across the transistor.


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