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 circuit for 40 V systems was found in a Linear Technology application manual. The circuit...
This circuit was obtained in a 90s Popular Electronics. In the table the values of the components...
This transmitter for the 7 MHz range, as we can assume by the number of turns of the coil, since the...