Sign ballasts provide power to light up high-output light bulbs used in indoor and outdoor signs. They can withstand cold temperatures and exposure to rain and other weather conditions. When one light bulb in the circuit fails, the other light bulbs will stay lit so the burnt-out bulb can be quickly identified and replaced. These ballasts are designed power specific quantities, types, and lengths of light bulbs. They 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.