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 was found in the January 1971 Radio Electronics magazine. It keeps the light flashing if...
This circuit was found in a Philips documentation from 1967. The circuit uses components from the...
This circuit, from 1999 documentation, prevents the powered device from receiving power when it...