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, from a 2002 documentation, checks the logic levels of the inputs, providing a...
Using a dual 555 CMOS this very useful circuit on the bench was found in the July 1998 Electronics Now...
The integrated circuit used in this regulator is quite old. Its 1970s casing is still made of...