The TORK 5021M Delayed Response Utility Grade MOV Surge Arrestor Photo Control is for use on streets, highways and other luminaries equipped with locking type receptacles, where most stringent surge protection is needed providing additional measures of safety and security by automatically turning your light on at dusk and off at dawn. Meets UL773 and ANSI C136.10 including color designations. Also meets EEI NEMA standards. The Surge Arrestor is 380 joule MOV (Metal Oxide Varistor) exceeds ANSI and NEMA requirements.