This circuit uses two relays that switch when the voltage exceeds the value given by zener D2. The circuit is from a Radio Electronics magazine from April 1975.
This small regulator was found in a Motorola 1968’s documentation. It is a current regulator using...
This circuit was found in a 1968 US publication. Transistors used are uncommon today. The circuit...
This electronic bait, or fish attractor, produces a sound in the water that attracts fish of...