Smart battery main switch prevents: battery discharge, fire hazard, theft, risk of short circuit! Our switch is made of solid metal. By loosening the thumbscrew, the starter circuit is interrupted. The supplied 30A bypass fuse receives the power supply for small electric loads such as clock, radio, alarm system or parking light. As a simple but highly effective anti-theft device, simply take the screw with you. If a car tries to start the vehicle, the fine-tuning device melts immediately and the electrical system of the vehicle is paralyzed. Since the ignition current (15) is also missing, the car can not be pushed.