私有综合服务网络（PISN）是一种专门为企业或组织内部提供通信服务的网络。PISN可以提供多种通信服务，如语音通话、传真、数据传输等。为了实现这些服务，PISN需要使用一种互换信令协议，以确保不同厂家的设备之间可以互相通信。ISO/IEC 13873:2003标准就是针对PISN互换信令协议中呼叫转移补充服务的规范。

呼叫转移是一种常见的通信服务，它可以将来电转移到另一个号码，以便用户在不同的地点或时间接听电话。ISO/IEC 13873:2003标准规定了呼叫转移补充服务的功能，包括无条件呼叫转移、有条件呼叫转移和无应答呼叫转移等。此外，该标准还规定了呼叫转移补充服务的信令流程，包括呼叫转移请求、呼叫转移确认和呼叫转移完成等。在信令流程中，PISN设备需要发送不同的消息格式和参数，以便其他设备可以正确地解析和处理。

ISO/IEC 13873:2003标准的实现可以带来多种好处。首先，它可以确保不同厂家的PISN设备之间可以互相通信，从而提高了通信的可靠性和稳定性。其次，它可以促进PISN设备的互操作性，使得用户可以更加灵活地选择不同的设备和服务。最后，它可以降低PISN设备的开发和维护成本，从而提高了整个行业的效益和竞争力。

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 Transfer supplementary service — 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 — Call Transfer supplementary service — 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 — Call Transfer supplementary service — 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 — Call Transfer supplementary service — Part 4: Test suite structure and test purposes
- ISO/IEC 11579-5:1995 Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Inter-exchange signalling protocol — Call Transfer supplementary service — Part 5: Abstract test suite