The electromagnetic spectrum has been widely used for broadcasting, telecom and data communications through intentional emissions of electro-magnetic fields. There have also been unintentional emissions from many electrical and electronic equipment, such as arc welding machines, household appliances and computer equipment. In order to protect the electromagnetic spectrum and to ensure compatibility of collocated electrical and electronic systems, regulatory bodies both within the United States and throughout the world community have established standards to control conducted and radiated electromagnetic interference in electronic equipment.