This strip protects against damaging electrical spikes and surges. It is designed to provide safe power, and to filter Radio Frequency (RFI) and Electromagnetic (EMI) interference. The light indicates that the unit is protecting against surges and spikes. This unit should be replaced if the light goes out. NOTE: This surge protector is not a lightning arrester and may not protect against direct lightning strikes. Use indoors only in a dry location. SPECIFICATIONS:3 line protectionNoise Reduction:EMI/RFI filters.Maximum surge dissipation:210 joules (8 x 20 microseconds)Electrical Rating:125V/15AMax Surge Voltage:330 voltsMaximum Spike Current:4500 AmpsResponse time:Less than 1 nanosecond