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。呼叫请求补充服务是PISN中的一种服务，它允许用户在呼叫过程中请求额外的服务。

ISO/IEC 20113:2004标准规定了呼叫请求补充服务的功能模型和信息流。该标准定义了呼叫请求补充服务的各种操作和参数，包括呼叫等待、呼叫保持、呼叫转移、呼叫拒绝等。此外，该标准还规定了呼叫请求补充服务的信息流，包括呼叫请求、呼叫请求确认、呼叫请求完成等。

ISO/IEC 20113:2004标准的实现可以提高PISN的效率和可靠性。通过使用标准化的呼叫请求补充服务，用户和服务提供商可以更加方便地进行通信，并且可以避免由于不同实现方式导致的兼容性问题。

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 -- Circuit-mode basic call control -- Part 1: Protocol specification
- ISO/IEC 11579-2:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Circuit-mode basic call control -- Part 2: Protocol implementation conformance statement (PICS) proforma
- ISO/IEC 11579-3:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Circuit-mode basic call control -- Part 3: Protocol implementation extra information for testing (PIXIT)
- ISO/IEC 11579-4:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Circuit-mode basic call control -- Part 4: Protocol implementation conformance statement (PICS) proforma -- Additional network feature
- ISO/IEC 11579-5:1995 Information technology -- Telecommunications and information exchange between systems -- Private Integrated Services Network -- Inter-exchange signalling protocol -- Circuit-mode basic call control -- Part 5: Protocol implementation extra information for testing (PIXIT) -- Additional network feature