The circuit shown was found in a 1967 RCA manual. Modern equivalent components can be used. The SCR must be according to the controlled load.
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...