We just had a customer email us with a good question about his 3-Cell Kit. He wants to use a three position toggle switch to control his car's ignition and starter. The switch is off in the down position, on in the middle and momentary in the up position. The switch that he wants to use is sold by Longacre Racing. Their part number is 45490.
This is an easy one to wire to the ISIS MASTERCELL. The common terminal on the switch gets tied to ground. The middle position gets connected to input 3 on the MASTERCELL. This is the white wire with the blue stripe. Input 4 on the MASTERCELL, the white wire with the yellow stripe, connects to the momentary terminal on the switch. As it is wired, the ignition input to the MASTERCELL will be on in the middle position and the starter input will be on in the momentary position. Since you need to have the ignition system powered when you are cranking the engine, you need to put a diode between the ignition and starter terminals. See the diagram for more details.
You can download this diagram and many others to help to wire your car from our reference library here.