Common sources of electromagnetic radiation : In general, radar systems, television, cell phone and radio transmission systems, radio frequency induction and media heating equipment, radio frequency and microwave medical equipment, a variety of electroprocessing equipment, communications transmission stations, satellite earth communication stations, large electric power generating stations, power transmission and substation equipment, high-voltage and ultra-high-voltage transmission lines, subway trains and electrical trains, and most household appliances are can produce various forms, different frequencies, different intensity of electromagnetic radiation sources.