This 555-based circuit was found in the August 1976 issue of Radio Electronics magazine. The tone frequencies are provided by the capacitors connected to the 555 IC.
This circuit uses an audio output transformer found in old transistor radios. Power output is...
Found in a 1967 Electronics World, this circuit uses unusual components today. The transformer has a high...
This circuit consists of a charge pump with positive input and negative output. We find it in a...