ETSI PRETS 300 064-1-1996 综合业务数字网(ISDN).直接拨入(DDI)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); Direct Dialling in (DDI) Supplementary Service; Digital Subscriber Signalling System No. One (DSS1) Protocol; Part 1: Protocol Specification Second Edition