Non-dimmable fluorescent ballasts are compatible with switches, occupancy sensors, and other lighting controls that turn lights on or off but do not dim their light output. They are used in fluorescent lighting fixtures in offices, retail stores, warehouses, convention centers, and other commercial spaces. Electronic ballasts are more efficient than magnetic ballasts and do not hum or cause fluorescent lights to flicker. Magnetic ballasts are used in older fluorescent fixtures. 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.