Ballasts are a rarely seen component of some lighting systems, however they play an integral role in making certain bulbs function well. A ballast is a device with two basic functions: 1) starting a bulb, and 2) controlling the electricity flow through the bulb. All gas-discharge bulbs, such as fluorescent tubes and high-intensity discharge (HID) bulbs, require an accompanying ballast to operate. Some fixtures have built in ballasts while others have it as a separate unit. When a bulb that uses a ballast is switched on, the ballast provides a quick burst of high voltage to establish an arc between two electrodes in the bulb. Once the arc is established, the ballast regulates the energy going into the bulb to help increase the bulbs efficiency, longevity and light output.

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