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.
This circuit is from an American 80's documentation. The transistor is general purpose,...
We found this circuit in the September 1971 issue of Radio Electronics magazine. The sensor is an...
This old configuration, using a unijunction transistor (UJT) controls a LED than blinks if an...