These RPM-Activated Switches will perform a variety of different functions from turning on a bulb or solenoid to activating an MSD Timing Control at a desired rpm.The RPM-Activated Switch, PN 8950, has two activation wires; one to ground a circuit and the other to open a circuit. Simply plug in an rpm module and wire the Switch to the circuit you want to activate. When the engine rpm reaches that amount, the circuit is activated and will remain on until the rpm falls below that amount.The RPM Window Switch, PN 8956, has two rpm adjustments; one to activate a circuit, while the other deactivates the same circuit. This Switch will supply then remove ground to a circuit. This is a great feature to deactivate nitrous before the engines rev limit is reached. Both Switches can be used with stock inductive ignitions or an MSD Ignition and can handle up to 1.5 amps. No rpm modules are supplied so they must be ordered from the selection of Modules shown on page 124. For use on 4, 6, or 8-cylinder engines. MSD RPM Activated Switches 8950 4 Cylinder Activate A Circuit At A Specific RPMUse With Stock Or MSD IgnitionsUse RPM Modules To Set RPM PointActivate Through Round Or 12 Volt ActivationRPM Modules Are Mint SuppliedPit Stop USAoffers MSD Ignition RPM Activated Switches 8950 at low everyday prices. Be sure to check out all of the products from MSD Ignition including MSD Ignition Parts and Accessories, MSD Ignition Parts and Accessoriess, MSD Ignition Parts and Accessories, MSD Switches, RPM Activated, MSD Fuel System and Intake Parts and Accessories, MSD Nitrous Oxide, MSD Nitrous Oxide System Components, MSD Nitrous Oxide Activation Switches, MSD Electrical System Parts and Accessories, MSD Switches, MSD Accessory Switches.