ISO/IEC 18051:2012规定了计算机支持电信应用第三阶段（CSTA）的服务和事件报告。 它专注于为交换功能、计算功能和特殊资源功能提供应用服务接口。CSTA应用程序接口与CSTA应用程序服务、观察或操作的各种用户网络接口和网络网络接口分离。由于CSTA间接地使用现有的电信接口进行操作，因此它的操作是通用的，因此各种现有接口之间的差异对CSTA应用程序是隐藏的。对用户到网络接口的支持不在CSTA的范围内。 尽管大多数终端设备（TE）适合与CSTA一起使用，但仍有TE在某些情况下不适用的情况。 ISO/IEC 18051:2012定义了允许在计算网络和电信网络之间进行功能集成的服务。支持此类功能集成应用的计算平台（即应用程序编程接口——API）不在ISO/IEC 18051:2012的范围内。 计算和交换（即电信）网络之间的通信可以通过从简单的点到点连接到局域网或广域电信网络的中间网络进行。 ISO/IEC 18051:2012是一套CSTA标准和技术报告的一部分，全面描述了应用、实施和利用基于CSTA的CTI应用程序所涉及的体系结构和实际问题。

ISO/IEC 18051:2012 specifies the Services and Event Reports for Computer-Supported Telecommunications Applications, Phase III (CSTA). It is focused on providing application service interfaces to a Switching Function, Computing Function and a Special Resource Function. A CSTA application interface is disassociated from the various user-network interfaces and network-network interfaces CSTA applications serve, observe or manipulate. Because CSTA operates with existing telecommunications interfaces indirectly, it operates generically so that differences among various existing interfaces are hidden from CSTA applications. Support of user-to-network interfaces is outside the scope of CSTA. Although most terminal equipment (TE) is suitable for use with CSTA, there will be instances of TE that will not be suitable in certain circumstances. ISO/IEC 18051:2012 defines services that allow functional integration between a computing network and a telecommunications network. Computing platforms (i.e., Application Programming Interfaces - APIs) that support such functionally-integrated applications are outside the scope of ISO/IEC 18051:2012. Communication between the computing and switching (i.e., telecommunications) networks can take place via intervening networks ranging from simple point-to-point connections to local- or wide-area telecommunications networks. ISO/IEC 18051:2012 is part of a suite of CSTA Standards and Technical Reports that provides a comprehensive description of the architectural and practical issues involved in applying, implementing, and utilizing CSTA-based CTI applications.