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 was found in an old publication and can be adapted for use with modern...
Rectangular signals up to a few hundred kilohertz can be generated with this circuit, which is...
The lie detector we presented was created by a professional detective and found in a 1982...