This circuit is from a 1968 documentation using one of the first integrated circuits available at the time, the TAA370. The circuit is powered by 1.3 V using a 200 ohm handset.
Also suitable for use as a noisy alarm, this Morse Code or telegraph practice oscillator was found...
This circuit makes simultaneous control of two up to 150 W incandescent lamps. The circuit is half wave...
This circuit was found in an old documentation from Europe. The integrated circuit used is...