私有综合服务网络（PISN）是一种专用的通信网络，用于在组织内部提供各种通信服务。PISN可以提供多种服务，如语音通信、数据传输、传真等。为了满足不同用户的需求，PISN需要提供一些补充服务，如呼叫优先级中断和呼叫优先级中断保护。

呼叫优先级中断是指在通话过程中，如果有更高优先级的呼叫进来，当前通话会被中断，以便更高优先级的呼叫能够得到及时处理。呼叫优先级中断保护是指在通话过程中，如果有更高优先级的呼叫进来，当前通话不会被中断，而是会被保护起来，直到更高优先级的呼叫处理完毕后再恢复通话。

ISO/IEC 15991:2003标准规定了呼叫优先级中断和呼叫优先级中断保护的功能模型和信息流。该标准定义了这些服务的基本功能和操作流程，以及与其他服务的关系。此外，该标准还规定了这些服务的参数和信令，以便不同厂商的设备能够互相兼容。

ISO/IEC 15991:2003标准的实施可以提高PISN的通信效率和可靠性，满足不同用户的需求。该标准适用于各种类型的PISN，包括基于ISDN、PSTN、IP等技术的网络。

相关标准
- ISO/IEC 11579-1:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Call-related supplementary services
- ISO/IEC 11579-2:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Call and circuit identification supplementary services
- ISO/IEC 11579-3:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Additional network feature supplementary services
- ISO/IEC 11579-4:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Advice of charge supplementary service
- ISO/IEC 11579-5:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Completion of calls to busy subscribers supplementary service