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.
The gain of this amplifier is controlled by light shining on an LDR. The circuit is from a Radio...
This circuit produces a whistle sound when acting on switch S1. Aids is applied to a transformer that is...
This filter that rejects a frequency range determined by the double-T was found in the August 1993...