从通信楼定时系统 BITS设备在同步网中的应用方式出发 ,介绍了 BITS设备 Clock-Star的设计原理和功能结构 ,并且重点分析了其中的直接频率合成 DDS技术的原理和特点 ,并给出了时钟设备的实际测试数据 This paper introduces the design principle and function structure of Clock-Star of BITS equipment from the application way of BITS equipment of communication building timing system in synchronous network, and analyzes the principle and characteristic of DDS technology of direct frequency synthesis in it, Actual test data of the clock device