Case Metal Oxide Varistors

A Varistor (or voltage-dependant resistor) is a component that varies its electrical resistance as the applied voltage changes. At low voltage they have a high electrical resistance and at high voltage a low electrical resistance. In a system they are ideal for diverting surge voltages and spikes away from critical components.
Metal Oxide Varistors (MOVs) are made from zinc oxide and other metal oxides placed between two metal plates or contacts. The functions and applications of these components are similar to standard varistors.