Designed to test the electrical system of an automotive vehicle running on 12V or 24V. One of the great features is being able to activate components with positive or negative without using a jumper wire. This would, for example, allow you to send voltage to a relay that controls whether or not a fan switches on. You can quickly test the voltage and polarity of a circuit or whether it's short or open, check continuity, locate cylinders which are misfiring, measure frequency of ignition pulses, test solenoids, lights and more. To top it all off the easy to read LCD is backlit so it's perfect for the dark crevices of an engine bay. All the features of a brand name unit at a fraction of the price.