This circuit was found in the Electronics Experimenter Handbook from 1991. The sensor is a diode and the circuit has a relay according to the voltage used in the supply.
This circuit, in addition to transforming a sinusoidal signal into a square, shifts its phase. The...
The transistors on this circuit can be the BC548. The circuit is from English documentation from...
In the figure we have three voltage doubler configurations that can be used in high and low...