This circuit detects when an audio signal exceeds a certain level or even occurs due to an object falling, a door slamming or other. The circuit is from a Radio Electronics from January 1980.
When this circuit is activated the LED flashes for a moment indicating that the function has been...
This 1970 Electronic Design circuit uses a varactor or varicap. The circuit divides the frequency...
Found in a 1993 Electronics Hobbyst Handbook, this passive circuit can be used with common...