This circuit is from a March 1978 Radio Electronics magazine article that showed how to build it. The circuit is TTL based and is powered. The components used can still be found.
This circuit is from 1968 documentation. We can assemble it with more modern components such as a...
Found in a 90s Silicon Chip documentation this circuit is intended to protect a speaker system in...
The UVTRON tube is an ultraviolet radiation sensor. In this circuit from Radio Electronics from...