ETSI PRETS 300 356-12-1994 综合业务数字网(ISDN).7号信令系统.用于国际接口的ISDN用户部分(ISUP)(版本2).第12部分:会议呼叫,追加(CONF)补充业务
Integrated Services Digital Network (ISDN); Signalling System No.7 ISDN User Part (ISUP) Version 2 for the International Interface Part 12: Conference Call, Add-on (CONF) Supplementary Service