This simple circuit found in a 1968 EEE was intended for data transmission over the telephone line. The components are from that time, some are uncommon today.
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...