This circuit was found in an English publication from 1967. The circuit is for listening on a phone. Transistors are types of germanium of the time.
This circuit was found in a Texas Instruments’ publication. The circuit must be powered from dual...
This circuit was obtained from an American publication of 1982, but can be easily assembled today...
This oscillator generates a sinusoidal tone of 1750 Hz determined by the twin-T. The circuit can be...