ETSI PRETS 300 138-1-1996 综合业务数字网(ISDN).闭合用户群(CUG)补充业务.数字用户1号信令系统(DSS1)协议.第1部分:协议规范(第2版)
Integrated Services Digital Network (ISDN); Closed User Group (CUG) Supplementary Service; Digital Subscriber Signalling System No. One (DSS1) Protocol; Part 1: Protocol Specification Second Edition