This circuit was found in the December 1976 issue of Radio Electronics magazine. The circuit includes a powerful pulsating siren. It is activated by courtesy light switches and other sensors.
This circuit was indicated in an old American publication to serve as a Laser alarm system as a...
This circuit, which uses only transistors as active components, was found in a 1987 documentation. The...
This sound meter or sonometer was found in a Popular Electronics from the 80's. The circuit can be...