Magnetic fluorescent ballasts are used to replace burnt-out magnetic ballasts in older fluorescent lighting fixtures. They are compatible with switches, occupancy sensors, and other lighting controls that turn lights on or off but do not dim their light output. The ballasts protect light bulbs from damaging power fluctuations that can reduce the quality of the bulbs' light output. They provide an initial spike of high voltage to turn on light bulbs and then regulate the current to the bulbs for as long as they are on. Replacement ballasts should have the same voltage and start type as the old ballast, be able to power the number and type of bulbs that are used in the fixture, and be capable of fitting into the fixture.