This circuit consists of an electrostatic sensor that can check if a cable is energized by simply approaching it. The circuit is from an Electronics Now from December 1998.
This amplifier for automotive use was found in the SGS manual of linear integrated circuits of...
This circuit was found in documentation from the 70s. We can try current JFET transistors....
This circuit makes use of a thermometric sensor that heats or cools according to a current of air....