欧美性生交xxxxx久久久,第九色激情,久久综合五月开心婷婷深深爱,国产精品亚洲专区在线观看,91精品国产综合久久青草,99国产在线视频,久久久久青草线蕉亚洲麻豆

A power line is a wire that carries current. The current transmission is usually point-to-point. Power cord can be divided into AC AC power line and DC DC power line according to the purpose. Usually, AC power line is wire rod with high voltage. Due to high voltage, this kind of wire can be formally produced after obtaining safety certification according to unified standard. The DC line is basically through the low voltage DC, so the safety requirements are not as strict as AC line, but for the sake of safety, countries still require unified safety certification.