This simple tester was found in a Popular Electronics from the 90s. The circuit is powered by two 9 V batteries since it requires a symmetrical source.
This circuit uses one UJT (Unijunction Transistor) to produce three different tones in a...
This circuit is from an 80's documentation, making use of PUTs that are not currently common...
June 2017 - The new touch switches C & K KXT series can now be obtained from Mouser Electronics. These...