ISO/IEC 13872:2003规定了补充业务呼叫转移无条件（CFU）、呼叫转移繁忙（CFB）、呼叫转移无应答（CFNR）和呼叫转移（CD），这些补充业务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-CFU、SS-CFB和SS-CFNR是在呼叫建立期间应用的补充业务，用于将传入呼叫转移到另一个目的地。SS-CD是一种补充服务，它允许服务用户通过请求将来电重定向到响应中指定的另一个号码来响应来电。 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 13872:2003包含呼叫转移补充业务的第1阶段和第2阶段规范。第一阶段规范（第6、7、8和9条）规定了PISNs用户所看到的补充服务。第2阶段规范（第10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 13872:2003 specifies the supplementary services Call Forwarding Unconditional (CFU), Call Forwarding Busy (CFB), Call Forwarding No Reply (CFNR) and Call Deflection (CD), which are applicable to various basic services supported by Private Integrated Services Networks (PISN). Basic services are specified in ISO/IEC 11574. SS-CFU, SS-CFB and SS-CFNR are supplementary services which apply during call establishment providing a diversion of an incoming call to another destination. SS-CD is a supplementary service which allows a served user to respond to an incoming call by requesting redirection of that call to another number specified in the response. Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. ISO/IEC 13872:2003 contains the stage 1 and stage 2 specifications of the Call Diversion supplementary services. The stage 1 specifications (Clauses 6, 7, 8 and 9) specify the supplementary services as seen by users of PISNs. The stage 2 specification (Clause 10) identifies the functional entities involved in the supplementary services and the information flows between them.