Charger protection relay (CB26312E)

This circuit was obtained from an Elektor magazine from the 90s. The circuit is to protect batteries while charging.

Microphone Preamplifier (CB26214E)
We found this circuit in Radio Electronics Special Projects from 1992. The circuit turns on the...
Surge Protector (CB18721E)
This circuit acts on a relay disconnecting the load when the input voltage exceeds the set limit....
Transistor MW Transmitter (CB19090E)
This experimental short-range transmitter came out in a 1972 publication and was designed to...