This circuit was found in a 1968 EEE. The circuit makes use of logic gates of the time and can be tested with equivalents from modern families.
This power supply, found in an Argentine publication from the 1970s, uses a wire potentiometer of 25 W or more...
This circuit was obtained from an English magazine from 1979, but can be easily assembled today...
The oscillator shown in the figure generates a 1 kHz tone that is reproduced on the speaker with...