Phone Message Flasher


Posted on Nov 25, 2012

This circuit flashes an LED to indicate that your phone rang during your absence. A differential amplifier with hyste


Phone Message Flasher
Click here to download the full size of the above Circuit.

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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