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TELEPHONE_VISUAL_RING_INDICATOR_1

2014-11-02 08:24  
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TELEPHONE_VISUAL_RING_INDICATOR_1
In this circuit, the ringing voltage on a telephone line causes NE-1 to break over, triggering SCR1, which in turn triggers SCR2. If a call has been received, depressing S2 will cause LED1 to light. Depressing S1 resets the circuit. This circuit has the advantage of lower battery drain because LED1 is not left on continuously after a ring signal, but only when S2 is depressed.