Found in a Hands On Electronics from the 80's this circuit allows the reading of low resistances in a common multimeter. The circuit consists of a constant current source.
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...