DIN EN 61643-21:2010
低压电涌保护装置.第21部分:接到通信和信令网络的电涌保护装置.性能要求和试验方法
Low voltage surge protective devices - Part 21: Surge protective devices connected to telecommunications and signalling networks - Performance requirements and testing methods, (IEC 61643-21:2000 + Corrigendum 2001 + A1:2008, modified); German version EN