This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and the coil can be made with 80 to 100 turns of fine enameled wire on a ferrite rod.
This circuit was found in a 90s Silicon Chip documentation. The current of the transformer is 1 A maximum,...
The output of this circuit using the NE5560 has the opposite polarity of the input voltage. The...
Found in an Electronic Design from the 90s, this sophisticated continuity tester uses operational...