We found this simple protection with zener diode in a 1967 Motorola documentation. The zener diode is 18 V, but the components can be changed for operation with other voltages.
Found in an American publication of 1968, this circuit makes use of a pilot light of the time. It...
This circuit was found in documentation from the 1980s requiring a variable power supply from 0 to...
This car alarm was found in an American '80s documentation. The circuit automatically activates...