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 simple expandable circuit was obtained from a Popular Electronics from the 80's. The supply...
This traditional configuration found in a Radio Shack document can use 2N2646. More keys can be...
This circuit was obtained in an Argentine publication in 1976. It consists of a series voltage...