UL is the abbreviation of Underwriter Laboratories Inc. in the United States. The UL Safety Testing Laboratory is the most authoritative in the United States and one of the larger private institutions in the world engaged in safety testing and appraisal. It is an independent, for-profit professional institution that conducts tests for public safety. It uses scientific testing methods to study and determine whether various materials, devices, products, equipment, buildings, etc. are harmful to life and property and the extent of the harm; determines, compiles, and publishes corresponding standards and materials that help reduce and prevent losses to life and property, and at the same time conducts fact-finding research business. UL certification is a non-mandatory certification in the United States, mainly focusing on the testing and certification of product safety performance, and its certification scope does not include the EMC (Electromagnetic Compatibility) characteristics of products.