Found in a 90s documentation, this circuit triggers the SCR when there is an overvoltage in order to cause the fuse to blow quickly. The SCR can be a TIC106.
This circuit is from an English magazine of 1977. The circuit is still current, just using BC547...
The adjustment of the maximum load voltage is made in the trimpot. The circuit is from 1994...
In the figure we have the conventional configuration of a differential amplifier with the...