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PCCC, Phòng cháy chữa cháy

Kết quả tìm kiếm trên "Tin tức": 1
...ever walked into a store and heard a bell go off as you crossed the threshold chances are it was caused by a photoelectric detector Behind the door on one side of the store is a light either a white light and a lens or a low-power laser and on the other side is a photodetector that can see...