This audio circuit was published in a Rado Electronics issue from October 1963. The transistors are from the time and the output is low impedance. Power is supplied with a voltage of 12 V.
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...