The BAL750C-4 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 BAL750C-4 instantly switches to the emergency mode and operates one or two of the existing lamps for 90 minutes. Provides a maximum initial lumen output of 750 lumens.