CB system is the first real international system for mutual recognition of safety test reports of electrical products. National certification bodies (NCBs) of various countries form multilateral agreements, and manufacturers can obtain national certification of other member countries of CB system with CB test certificate issued by one NCB. CB system is based on international IEC standards. If the national standards of some member countries are not completely consistent with IEC standards, the existence of national differences is also allowed, but it should be published to other members. CB system uses CB test certificate to verify that the product sample has successfully passed the appropriate test, and conforms to the relevant IEC requirements and the requirements of the relevant member states. The main goal of CB system is to promote international trade, which means to make manufacturers closer to the ideal goal of "one test, multiple applications" by promoting the unified coordination of national standards and international standards and the cooperation of product certification bodies. At present, EMC is not included in CB system.