Found in documentation from the 90s, this circuit triggers a relay with inductive signals applied to a link. The sensitivity depends on the frequency and the power supply depends on the relay used.
This circuit was found in a 1964 documentation. It shows how to achieve automatic gain control for...
Using transistors at the time, this circuit was found in a 1967 Ferranti documentation. The...
This circuit, which controls both the temperature and the level of a liquid in a reservoir, was...