Lighting ballasts control the starting and operating voltages of electrical gas discharge lamps, also known as compact fluorescent lamps (CFL). Because they do not have an intrinsic feedback mechanism that limits operating current like the positive temperature coefficient of resistance of the filaments of incandescent light bulbs, gas discharge lamps need a ballast to limit electric current. Modern electronic lighting ballasts use solid-state circuitry to transform the voltage and alter the frequency of the supplied power. This eliminates any flickering of the CFL and regulates power more efficiently than is possible with standard magnetic lighting ballasts.