This circuit can be used with 5 to 15 V sources and the zener diode must be chosen according to the trip voltage of the protector. The circuit blows the fuse when the voltage exceeds the zener value.
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...