The ballast prevents too much electricity from flowing through the tube. It also starts the lamp with a high voltage for a split second when it is switched on. The ballast is located inside the fixture in traditional fluorescent tube fixtures. In compact fluorescent bulbs the ballast is in or near the base of the bulb. There are two types of ballasts, magnetic and electronic. Magnetic ballasts have mostly fallen out of use, as they are less efficient than electronic ballasts, they cause the bulb to flicker, and they do not start instantly. Electronic ballasts were at one time more expensive than magnetic ballasts, but now the price is about the same.