The tester simply plugs inline on the 6-pin Weatherpak connector of most E6 ignitions and is supplied with a load/test plug that you install on the coil wire at the distributor cap. With the ignition on, you can simulate a trigger signal that fires the ignition and coil. From there you can compare the tester?s accurate digital readout with the tachometer and also test the function of any RPM activated switch such as for a nitrous solenoid or shifter. A very useful tool to have on hand.