The BALT5-500ACTD Fluorescent Emergency Ballast allows the same fixture to be used for both normal and emergency operation when used in conjunction with the AC ballast. If used in an emergency only fixture, no AC ballast is necessary. In the event of a power failure, the BALT5-500ACTD instantly switches to the emergency mode and operates one of the existing lamps for 90 minutes. Provides a maximum initial lumen output of 500 lumens.