同义词
1)Synchronous Digital Hierarchy(SDH ),同步数位阶层2)digital cross connect Ssstem equipment(SDH-Based),同步数位阶层数位交换连接3)Digital Cross Connect System Equipment(SDH-Based),同步数位阶层数位交换连接系统设备4)optical/digital loop carrier equipment(SDH-Based),同步数位阶层光数位回路载波5)SDH(Synchronous Digital Hierarchy),同步数位阶级6)hierarchy,synchronous digital (SDH),同步数字层阶架构
