This circuit appeared in Radio Elecronics magazine in 1968. The operating circuit is a general-purpose type at the time and the power supply must be symmetrical.
The circuit is from American documentation from the 1980s. Operational ones are not common today,...
This simple continuity tester consists of an oscillator found in the 1983 Electronics Experimenter Special...
This circuit is from a 70s linear integrated manual. The integrated circuit used is uncommon today...