亚洲国产99999在线精品一区|国产精品186在线观看在线播放|久久久一本精品99久久精品97|精品国产污污免费网站入口在线看|精品久久久久无码中文字幕东京热|97久久天天综合色天天综合色hd|无码午夜人妻一区二区三区不卡视频

Early network cabinets were mostly made of castings or angle steel joined by screw, rivet or welded into cabinet frame, together with cover plates (doors) made of thin steel plates. This kind of network cabinet is large, bulky and simple in appearance, and has been eliminated.

With the use of transistors and integrated circuits and the miniaturization of various components and devices, the structure of cabinets is also developing towards miniaturization and building blocks. Network cabinet has been developed from the whole panel structure to the plug-in structure with a certain size series. Inserts and plug-ins are arranged horizontally and vertically. Thin steel sheet, steel profiles of various cross-section shapes, aluminum profiles and various engineering plastics are widely used in network cabinet materials. In addition to welding and screw connection, the frame of network cabinet also adopts bonding technology.