ISO/IEC 15052:2003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参考点处支持召回补充业务（SS-RE）的信令协议。 SS-RE是一种补充业务，如果呼叫无人应答，它可以将已转移的呼叫重新定向回服务用户。SS-RE仅适用于通过连接进行传输后，而不适用于通过重新路由进行传输后。 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。本国际标准包含Q参考点的第3阶段规范，并满足ISO/IEC 15051中第1阶段和第2阶段规范确定的要求。 SS的信令协议- 按照ISO/IEC 11572中的规定，RE在基本电路交换呼叫控制的信令协议之上运行，并使用ISO/IEC 11582中规定的补充业务控制通用程序的某些方面。 ISO/IEC 15052:2003还规定了额外的信令协议要求，以支持SS-RE和其他补充业务与ANF之间Q参考点的交互。然而，与呼叫转移补充业务的交互被指定为SS-RE信令过程的一部分，因为它是召回补充业务的基本方面。 注:对Q参考点的信令协议没有影响的其他交互可在相关的1级规范中找到。 ISO/IEC 15052:2003适用于可相互连接以形成PISN的PINX。

ISO/IEC 15052:2003 specifies the signalling protocol for the support of Recall supplementary service (SS-RE) at the Q reference point between Private Integrated services Network eXchanges (PINXs) connected together within Private Integrated Services Network (PISN). SS-RE is a supplementary service which provides for the re-direction of a transferred call back to the served user if the call is unanswered. SS-RE is only applicable after transfer by join, not after transfer by rerouteing. 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. This International Standard 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 15051. The signalling protocol for SS-RE 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 15052:2003 also specifies additional signalling protocol requirements for the support of interactions at the Q reference point between SS-RE and other supplementary services and ANFs. However, the interaction with the Call Transfer supplementary service is specified as part of SS-RE signalling procedures as it is the essential aspect of the Recall supplementary service. NOTE Additional interactions that have no impact on the signalling protocol at the Q reference point can be found in the relevant stage 1 specifications. ISO/IEC 15052:2003 is applicable to PINXs which can be interconnected to form a PISN.