This complex circuit was found in the 1993 edition of the Electronics Experimenter's Handbook. Most of the components are still common today.
This source was found in a 1982 American publication, but can be easily assembled using 2N2995 (PNP...
This contact or reed switch actuation was found in a 1964 Electronic Design. The circuit can be...
Found in a 1968 Electronics World, this circuit uses components from the era. In this circuit, a...