Legislation for power factor has been in place for over 100 years with rules in 1899 to prevent incandescent light bulbs from flickering. 30 years ago, the international standards body, IEC, published IEE 555-2 to limit harmonics through power factor correction and IEE 555-3 to cut disturbances caused by household appliances. Today, more stringent legislation is in place to govern power factor. The EU implements EN61000-3-2 for equipment with a power supply rated between 75W and 600W. This sets limits to the 39th harmonic for equipment with input currents less than or equal to 16A per phase. Split into four classes, A, B, C and the most stringent class, D. In the US, the Energy Star guidelines call for computing equipment to have a power factor of 0.9 or higher at 100 percent of rated output in the PC's power supply. This means computing equipment with internal power supplies require the use of active power factor correction. Legislation has also come into force around the world with more stringent regulations coming into effect for China, Japan, and Australia also based on the EN61000-3-2 standard.