DIN ETS 300746-1997 传输和多路传输技术(TM).同步数字分级(SDN).网络保护示意图.自动保护开关.APS协议和APS操作
Transmission and Multiplexing (TM) - Synchronous Digital Hierarchy (SDH) Network protection schemes - Automatic Protection Switch; APS protocols and operation; English version ETS 300746:1997