This inductance bridge uses an external audio signal. The circuit is from a Radio Electronics from January 1966. The instrument can be a common multimeter in the lowest current range.
The output power of this wireless intercom for the 27 MHz (11 meters) range is in the order of ½ W,...
In the figure we have the way to implement an Exclusive OR or XOR gate with CMOS or TTL...
This useful circuit is used to test the insulation of cables, appliances, leaks in high voltage...