Found in old documentation, this circuit uses a double gate MOSFET. The operating frequencies depend on the coil, and the indicator is a microammeter.
This precision circuit, which also functions as a bridge, was found in a February 1967 Popular...
This circuit was found in a publication from the 90s. The circuit can be assembled with modern...
A first circuit that uses a phototransistor as a detector and is suitable for covering short...