The functionality of a ZNR® surge absorber can be compared to that of ON/OFF switch. Under normal power supply voltage conditions, ZNRs have high resistance, like a switch in the OFF state. The ZNR does not affect the power supply voltage or signal quality. When a surge occurs, the resistance value drops, like a switch in the ON position. The ZNR controls the surge voltage by passing the excessive current to ground (GRD) through the ZNR, thus protecting the electronic equipment from the dangerous surge. The surge energy absorbed by the ZNR® is converted to exothermic heat. The handling capability, or amount of surge the ZNR can handle, depends on the volume of the ZNR. The larger the ZNR, the higher the surge energy it can absorb. When not using a ZNR surge absorber, electronic equipment can be damaged or broken by any high voltage surge.