The switch type surge protector is a gap discharge type device, and its lightning energy discharge capability is large. The main function used on the line is to discharge lightning energy; the voltage limiting surge protector is a zinc oxide varistor device, and its lightning energy The ability to discharge is small, but its overvoltage suppression capability is good. The main use on the line is to limit overvoltage. Because of this, switch-type surge protection such as the Asafe series is generally used at the entrance of the building to discharge the lightning energy. Then, in the latter stage, a limiting voltage surge protector such as the AM series is used to limit the lightning energy due to the front stage. After the diarrhea, the high overvoltage generated in the rear line. Two surge protectors need to be used together to ensure the safety of the equipment in the distribution line.