The configuration shown was found in the October 1974 Radio Electronics magazine. The integrated circuit used is the CD4001 and the power supply depends on the application.
Found in an EDN from the 80's, this circuit makes use of an operational one of the time. The...
This circuit can either directly supply a piezoelectric transducer (BZ) or a stage with a...
Only for reference this is a circuito f a commercial receiver of the year 1958. The circuit uses...