DIN EN 60721-3-4:1995
環境條件分類.第3部分:環境參數組分類及其嚴酷程度分級.第4節:在無天氣防護位置固定使用的產品
Classification of environmental conditions - Part 3: Classification of groups of environmental parameters and their severities - Section 4: Stationary use at non-weatherprotected locations (IEC 60721-3-4:1995); German version EN 60721-3-4:1995