Found in a radio amateur magazine of the 1980s, this circuit uses components that can still be found easily. The circuit is for NiCad batteries.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...