The Nitrous Express digital rpm window switch is an innovative module that monitors engine rpm as well as throttle position to automatically activate your nitrous system based on user adjustable RPM and TPS values. This ensures that the nitrous activates only within the set RPM and TPS values. The large LCD display has an adjustable contrast screen this changes how dark the numbers and letters appear. Another great feature of the window switch is the RPM filter is a noise filtering feature to help with ignition noise on newer vehicles. If you notice an erratic RPM Signal you will want to enable the RPM filter feature. This module is compatible with all 1 to 12 cylinder engines with coil on plug, waste spark, distributor or crank trigger equipped ignition systems.