SCR Complete alarm (CB20474E)

This circuit is from a Popular Electronics from 1992. It uses two SCRs and can be triggered by sensors in series and in parallel.

Powerful current converter (CB5096E)
This circuit can convert an AC voltage signal into a current up to 1 A for powering a load. The...
Continuity Tester (CB4546E)
This continuity tester for low resistances was found in an English magazine from 1978. The circuit...
Liquid Level Control (CB5311E)
The purpose of this circuit is to maintain the liquid level of a reservoir between two values...