Found in Radio Electronics from the 90s, this siren finds many variations on this site. The transistor must be equipped with a heat radiator.
This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V...
This circuit was found in a PC documentation from 1996. It can be used as a shield with modern...
This limit alarm was found in a 1980s US documentation. Comparators can be equivalent and the...