ISO/IEC 13874:2003规定了在专用综合业务网络（PISN）内连接在一起的专用综合业务网络交换机（PINX）之间的Q参考点处支持路径替换附加网络功能（ANF-PR）的信令协议。 ANF-PR是一种适用于已建立呼叫的功能，允许该呼叫在PINX之间的连接被新连接取代。 ISO/IEC 11579-1中定义了Q参考点。 按照ETS 300 387规定的方法，分三个阶段制定服务规范。 ISO/IEC 13874:2003包含Q参考点的第3阶段规范，并满足ISO/IEC 13863中第1阶段和第2阶段规范确定的要求。 根据ISO/IEC 11572的规定，ANF-PR的信令协议在基本电路交换呼叫控制信令协议的基础上运行，并使用ISO/IEC 11582规定的补充业务控制通用程序的某些方面。 ISO/IEC 13874:2003还规定了支持ANF之间Q参考点处交互的附加信令协议要求- 公关和其他补充服务以及ANF。 ISO/IEC 13874:2003适用于可互连形成PISN的PINX。

ISO/IEC 13874:2003 specifies the signalling protocol for the support of the Path Replacement additional network feature (ANF-PR) at the Q reference point between Private Integrated services Network eXchanges (PINXs) connected together within a Private Integrated Services Network (PISN). ANF-PR is a feature which applies to an established call, allowing that call's connection between PINXs to be replaced by a new connection. The Q reference point is defined in ISO/IEC 11579-1. Service specifications are produced in three stages and according to the method specified in ETS 300 387. ISO/IEC 13874:2003 contains the stage 3 specification for the Q reference point and satisfies the requirements identified by the stage 1 and stage 2 specifications in ISO/IEC 13863. The signalling protocol for ANF-PR operates on top of the signalling protocol for basic circuit switched call control, as specified in ISO/IEC 11572, and uses certain aspects of the generic procedures for the control of supplementary services specified in ISO/IEC 11582. ISO/IEC 13874:2003 also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between ANF-PR and other supplementary services and ANFs. ISO/IEC 13874:2003 is applicable to PINXs which can interconnect to form a PISN.