私有综合服务网络（PISN）是一种专门为企业或组织内部通信而设计的通信网络。PISN可以提供多种通信服务，如语音通信、数据传输、传真等。为了实现这些通信服务，PISN需要一种互换信令协议，以便不同的设备和系统之间进行通信。ISO/IEC 15054:2003标准就是针对PISN的互换信令协议的呼叫拦截额外网络功能的规范。

呼叫拦截是一种常见的通信功能，它可以在通信过程中拦截呼叫并进行处理。例如，当一个电话用户拨打一个被拦截的号码时，呼叫拦截功能可以将呼叫转接到其他号码或者拒绝呼叫。在PISN中，呼叫拦截功能也是非常重要的，它可以帮助企业或组织更好地管理通信流量和保护通信安全。

ISO/IEC 15054:2003标准规定了PISN中呼叫拦截的实现方式。具体来说，该标准规定了呼叫拦截的触发条件、呼叫拦截的处理流程、呼叫拦截的通知方式等。例如，当一个电话用户拨打一个被拦截的号码时，PISN可以根据预设的规则进行呼叫拦截。呼叫拦截的处理流程包括拦截呼叫、通知被拦截方、记录呼叫信息等。呼叫拦截的通知方式可以是语音提示、短信通知等。

ISO/IEC 15054:2003标准的实现可以带来多种好处。首先，呼叫拦截功能可以帮助企业或组织更好地管理通信流量，避免通信拥堵和资源浪费。其次，呼叫拦截功能可以保护通信安全，防止恶意攻击和信息泄露。最后，呼叫拦截功能可以提高通信效率，使得通信更加便捷和高效。

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 Completion supplementary services — Part 1: Completion on busy and on no reply
- ISO/IEC 11579-2:1995 Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Inter-exchange signalling protocol — Call Completion supplementary services — Part 2: Completion on no reply to call waiting
- ISO/IEC 11579-3:1995 Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Inter-exchange signalling protocol — Call Completion supplementary services — Part 3: Completion on no reply to call deflection
- ISO/IEC 11579-4:1995 Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Inter-exchange signalling protocol — Call Completion supplementary services — Part 4: Completion on busy to call waiting
- ISO/IEC 11579-5:1995 Information technology — Telecommunications and information exchange between systems — Private Integrated Services Network — Inter-exchange signalling protocol — Call Completion supplementary services — Part 5: Completion on busy to call deflection