Integrated Services Digital Network (ISDN); Signalling System No.7; ISDN User Part (ISUP) version 2 for the international interface; Part 16: Call Hold (HOLD) supplementary service [ITU-T Recommendation Q.733, clause 2 (1993), modified]
综合业务数字网(ISDN);七号信令系统;国际接口的ISDN用户部分(ISUP)第2版;第16部分:呼叫保持(Hold)补充业务[ITU-T建议Q.733 第2条(1993) 修改]