It's applicable to an electric line of AC 50Hz or 60Hz. Rated working voltage 380V or less it is used to limit the transient over-voltage amplitude and to absorb, dissipate and discharge the surge current energy. If the product is used in a high-class over-voltage condition, it can degrade the over-voltage class borne by the protected electric element to the next lower class. It is also applicable to form a packaged electric appliance with a modulus terminal electric device, raising the erection class and expanding the application range of the eletric device, raising the erection class and expanding the application range of the electric appliance. If the product is used for the terminal devices, it can further reduce the over-voltage due to improper operation or light-stroke voltage to protect computer and microcomputer and household appliance.