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.
We found this circuit, which appears with variations on this site, in a European documentation from the...
This circuit that drives an electromechanical counter of the time was found in Radio Electronics magazine...
Found in a Hands On Electronics of the 80s, this circuit makes use of a gas sensor of the time....