Found in American documentation from the 90s, this circuit uses a high voltage relay and has no grid isolation. The high values of R1 and R2 prevent the shock when it touches the sensors.
This railroad model circuit was found in a 1960 Sylvania transistor manual. The components are from that...
This circuit samples the current in a load and in case of excessive value it activates a...
We found this circuit in a 2004 documentation. The circuit consists of a standard lamp for testing...