This circuit can be adjusted between 0.2 and 2 V to trigger with chosen voltages comparing them with the input voltages. We found it in a 1967 documentation.
This circuit was found in a 1980s documentation but can be easily assembled even today by the...
This circuit makes use of a stroboscopic tube, a component that no longer exists today. The...
This circuit for incandescent light bulbs was suggested by General Electric in a 1980s...