Still looking for that extra margin of safety when using your NOS nitrous kit? If you have a Ford DIS (Distributorless Ignition System), then here's the answer. The DIS window switch uses two RPM ''pills'' that turn the system ''on'' and ''off''. This enables users to avoid the danger of engaging the nitrous system at to low of an RPM, and leaving the nitrous system enabled past the engine's rev-limit. This is especially dangerous on late-model vehicles that cut the fuel injectors instead of the ignition to limit engine RPM.