For positive protection of electrical or electronic equipment, use this against excessive supply voltage. Because of incorrect switching, electrical wiring, short circuits, or failure of regulators, an electronic crow-bar circuit can quickly place a short circuit through the power lines, thereby decreasing the voltage across the protected device to close to zero and blowing a fuse. The triac and SBS both are bilateral components, the circuit will be equally useful on alternating current or direct current supply lines.
An alarm unit such as the Mallory Sonalert may be connected across the fuse to provide an audible indication of crowbar action. (This circuit may not act on short, infrequent power line transients).