This high sensitivity circuit was found in the July 1992 Radio Electronics magazine. The circuit drives a buzzer, but a relay can be used to activate an external load.
This circuit was obtained from a 1978 English magazine. This circuit can be easily assembled. We...
This circuit was found in American documentation from the 1980s. The integrated circuit used is a...
This sophisticated comparator, which may have didactic or practical purposes, was found in a 1980s...