准同步数字系列
- 网络pdh;Plesiochronous digital hierarchy;PDH Plesiochronous digital hierarchy
准同步数字系列-
电信传输方式自模拟转变为数字以来，一直沿用的是PDH（PlesiochronousDigitalHierarchy，准同步数字系列）传输方式。
After telecom communicaton 's style changed from analog to digital , the communication mode had been PDH ( Plesiochronous Digital Hierarchy ) .
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SDH具有全世界统一的网络节点接口，标准化的信息等级结构，能够兼容现有的PDH准同步数字系列传输系统，使得全世界传输系统能够在STM-N级别上进行互联互通。
SDH has the unified network node interface ( NNI ), standardized information class structure in all the world and can be compatible with PDH , which makes all the transmission network systems can communicate with each other on the level of STM-N.