Charger protection relay (CB26312E)

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

Small fluorescent inverter (CB5300E)
The purpose of this circuit is to power a small fluorescent lamp from from a 12 V battery. The circuit...
Darlington Stage with Feedback (CB975E)
This circuit was found in a 1968’s publication and uses germanium transistors. Equivalents can be...
Busy Tone Generator (CB13937E)
This circuit generates the busy tone of ordinary telephones. The transistors can be the BC548 and...