Phone Message Flasher

  

Posted on Nov 25, 2012    9566

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.




Leave Comment

characters left:

New Circuits

.