This 1968 Mallory circuit uses an uncommon integrated circuit today. The circuit has a 30 to 20,000 Hz response with lower power and is powered by 12 V.
This circuit emits a sound when a magnetic field, of a magnet, for example, approaches the sensor....
Simple timers can be designed using inverters or any other gate that can be connected as inverter. Figure...
This circuit was obtained from an American documentation from 1976. The circuit can be adapted to...