APC SurgeArrest Essential 7 Outlet Surge Suppressor undergo stringent testing by IEEE, and is awarded"let-through ratings", which indicate the maximum voltage level that can possibly reach your equipment after a surge or voltage spike has passed through a surge protector. This Surge Suppressor attenuates EMI/RFI line noise that can cause data errors and keyboard lockups, ensuring better performance of protected equipment. SurgeArrest components such as MOVs and Thermal fuse ensure instantaneous reaction to lightning strikes and wiring faults. If the surge components are damaged due to power spike or over voltage, excess power cannot reach your equipment.