Transistor Overvoltage Crowbar Protector

This is a transistor crowbar circuit for overvoltage protection. This circuit is used to protect any devices, when the overvoltage occurs. This circuit consist of diode, transistor, and resistor, and a fuse.  The device that needs to be protected should be connected in parallel with the transistor. The 1N87 diode cut off the transistor across supply line until overvoltage occur. When the supply voltage rises above a certain level, the current will pass the diode and and flow through transistor’s base-emitter, so the transistor will short the blow the fuse to protect the device. Here is the schematic diagram of the circuit: