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.
Based on FET operational amplifiers, this circuit was found in a manufactirer documentation. The...
This circuit, obtained from a 1965 magazine, can still be assembled using some modern equivalent...
This circuit uses an operational amplifier that is still common today. The indication is made by...