This circuit with germanium transistors is from 1960 and was found in Mullard's transistor application manual from 1960. The circuit can be adapted to use more modern transistors.
This 1995 circuit uses interruption sensors or NC connected in series in any quantity. With the...
This circuit, suggested by a 1975 documentation, detects an electrical discharge in a storm by...
Found in an old Electronic Design, this circuit provides an output voltage that is the absolute...