Phone Message Flasher

  
This circuit flashes an LED to indicate that your phone rang during your absence. A differential amplifier with hyste
Phone Message Flasher - schematic

resis (Ql, Q2, and Q3) detects high line voltage (ringing), which turns on Q4, multivibrator Q5/Q6, and flashes the LED via Q7. Ql and Q2 remain on until the phone-line voltage drops to less than 9 V, which indicates an off-hook condition.




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