The AV Power Protection line of surge protectors are designed to protect your audio / video equipment from damaging power spikes and interference found in all electrical power sources. When a power surge hits, the surge protector dissipates the incoming and outgoing voltage to a level that will not damage your equipment. The built in indicator light identifies when the surge protector is working to protect your equipment - when the indicator light is no longer illuminated, your surge protector need to be replaced.