This circuit was originally intended for reading movie soundtracks. The circuit is from 1967 and was found in an English publication. The sensor is semiconductor type.
This circuit is designed to activate an automotive alarm after 8 minutes of activation. Of course...
This circuit consists of a simplified Hartley oscillator that changes the frequency according to...
Integrated circuits 8038 and 8063 are not common today. This circuit, found in the 1983 Intersil...