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. Unlike the APC SurgeArrest products, most surge suppressors continue to let power through even after circuits have been damaged, leaving your equipment exposed to other damaging surges.Protection of data lines (Ethernet, Coaxial and Phone lines) ensures complete protection of your equipment from surges. It is very important to protect your equipment from “back door” electric surges traveling through data lines, as they can be as damaging to your equipment as surges traveling over power lines.The 'Institute of Electrical and Electronics Engineers' (IEEE) Let-Through Voltage rating is based on a test that subjects a Surge Protector to a 6,000 volt spike. The rating equates to the amount of excess voltage that reaches connected equipment. The lower the number, the better the performance of the Surge Protector is. Underwriter's Laboratory's UL1449 surge protection safety standard uses these ratings to help users gauge performance. UL's best Transient Voltage Surge Suppressor (TVSS) Let-Through Voltage rating is "300V".APC surge protectors undergo stringent testing by IEEE, and are 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 an electric surge protector. Lower IEEE let-through ratings indicate better protection and performance. The APC Essential SurgeArrest series offers optimal performance with a let-through rating of less than 330V for North American products, and a rating of less than 15% for products sold worldwide. All APC products comply with local agency safety requirements, including UL in North America and CE/Kema/Gost/C-tick/A-Tick/Telepermit in their respective regions.