Transmission and multiplexing - generic requirements for synchronization networks - part 6 - 1 : timing characteristics of primary reference clocks endorsement of the english version en 300462 - 6 - 1 v 1 . 1 . 1 1998 - 05 as german standard 传输和多路复用.同步网络的一般要求.第6 - 1部分:原始