Professional FIA Battery Master Switch is the best quality switch of its type available.
European manufactured with silver plated contacts and a high quality relay to ensure the highest possible levels of reliability Mandated for most forms of motorsport these switches prevent the possibility of damage to the alternator due to voltage surge caused by disconnecting the battery whilst current is still being generated. When the red key is turned to the Off position the engine is stopped as the contacts are also broken thereby cutting the ignition circuit, simultaneously the contacts create a circuit through the resistor to allow the alternator to safely discharge its residual current to earth.