ISO/IEC 13865:2003规定了补充业务呼叫转移（SS-CT），它适用于专用综合业务网（PISN）支持的各种基本业务。ISO/IEC 11574规定了基本服务。 SS-CT是一种补充业务，用户可以将该用户的两个呼叫（其中一个必须应答）转换为两个呼叫的其他两个用户之间的新呼叫。 根据ETS 300 387中描述的方法，补充业务规范分三个阶段生成。ISO/IEC 13865:2003包含SS-CT的第1阶段和第2阶段规范。第一阶段规范（第6条）规定了PISNs用户看到的补充业务。第2阶段规范（第7条和第8条）确定了补充服务中涉及的功能实体以及它们之间的信息流。 ISO/IEC 13865:2003包含两个第2阶段规范，反映了网络内运行服务的不同方式:通过连接传输和通过重新路由传输。

ISO/IEC 13865:2003 specifies Supplementary Service Call Transfer (SS-CT), which is applicable to various basic services supported by Private Integrated Services Networks (PISNs). Basic services are specified in ISO/IEC 11574. SS-CT is a supplementary service which enables a user to transform two of that user's calls (of which one must be answered) into a new call between the other two users of the two calls. Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. ISO/IEC 13865:2003 contains the stage 1 and stage 2 specifications of SS-CT. The stage 1 specification (clause 6) specifies the supplementary service as seen by users of PISNs. The stage 2 specification (clauses 7 and 8) identifies the functional entities involved in the supplementary service and the information flows between them. ISO/IEC 13865:2003 contains two stage 2 specifications reflecting different ways of operating the service within the network: transfer by join and transfer by rerouteing.