This is a Japanese commercial radio from the 60s. The superheterodyne circuit of 7 transistors for medium waves has 200mW of output when powered by 4 common batteries.
This simple circuit was found in a 1981 publication. As readers can see, we have an H switch and...
This circuit is from 2001 documentation with the purpose of controlling a pump that fills a water...
This simple CMOS metronome circuit can be mounted in a small box, providing both sound and light...