信息技术.系统间远程通信和信息交换.专用综合业务网.规范、功能模式和信息流.呼叫优先中断和呼叫优先中断保护补充业务

[中文适用范围]： 本国际标准规定了补充业务呼叫优先中断（SS-CPI）和呼叫优先中断保护（SS-CPIP），适用于专用综合业务网络（PISN）支持的各种基本业务。 基本服务在 ISO/IEC 11574 中规定。 注 1 - 本国际标准的该版本不适用于电路模式多速率承载服务。 SS-CPI是一项补充业务，允许在没有可用用户信息信道的情况下成功进行优先呼叫的呼叫请求。 这是通过强制释放已建立的较低优先级呼叫来实现的。 SS-CPIP 是一项补充服务，可以保护呼叫免受其他优先呼叫的干扰。 由于SS-CPI是主叫用户使用的业务，而SS-CPIP是主叫用户或被叫用户使用的业务，因此将SS-CPI和SS-CPIP分开描述。 根据 ETS 300 387 中描述的方法，补充服务规范分三个阶段制定。 本国际标准包含 SS-CPI 的第一阶段和第二阶段规范。 第一阶段规范（第 6 条）指定了一般功能原则和功能。 第 2 阶段规范（第 7 条）标识了补充服务中涉及的功能实体以及它们之间的信息流。 [外文原描述]： ISO/IEC 15991:2003 specifies the Supplementary Services Call Priority Interruption (SS-CPI) and Call Priority Interruption Protection (SS-CPIP), which are applicable to various basic services supported by Private Integrated Services Networks (PISN). Basic services are specified in ISO/IEC 11574. NOTE This edition of ISO/IEC 15991 does not apply to the circuit-mode Multiple Rate Bearer Service. SS-CPI is a supplementary service that allows a call request for a priority call to proceed successfully in the case that there is no user information channel available. This is accomplished by force releasing an established call of lower priority. SS-CPIP is a supplementary service that allows for the protection of calls against interruption from other, priority, calls. SS-CPI and SS-CPIP are described separately because SS-CPI is a service used by a calling user, and SS-CPIP is a service used by either a calling user or a called user. Supplementary service specifications are produced in three stages, according to the method described in ETS 300 387. ISO/IEC 15991:2003 contains the stage 1 and stage 2 specifications of SS-CPI. The stage 1 specification (clause 6) specifies the general feature principles and capabilities. The stage 2 specification (clause 7) identifies the Functional Entities involved in the supplementary service and the information flows between them.