Electronic Sign Ballast, Fluorescent, Input Voltage: IntelliVolt operation; 120V to 277V, Instant Start, SignPro Series. For use with any 1 to 4 lamp T12HO lamps up to 10 feet long, 10 feet to 40 feet total length. For use with any 1 to 4 lamp T8HO lamps up to 8 feet long, 8 feet to 32 feet total length. For use with T12HO / T8HO lamps or any combination of lamps in circuit as long as total length per circuit does not exceed 9 feet for T12HO and 7 feet for T8HO. *** NOTE: Fixture/Lamp Holders may need to be rewired! See cut sheet wiring diagram ***