The switch works the way that if it's on "0" then both circuits are opened, rocking it to I or II positions is switching on two separate circuits. One for cutting off the engine - electrovalve on injection pump (diesel), second one starts the engine with a starter. if it's in "0" it works like a normal oem setup. I've used two relays one normally opened for a starter, second one is normally closed for feeding current to electrovalve. So when I press the button is switches relay from normally closed to open position and electrovalve cuts off the fuel.
It works great. I have to control over the engine with just my thumb.
