It also calculates theoretically the minimal time interval between two trains in quasi - moving - block signaling system and recommends approximate values for the length of coded digit track circuit . the rapid development of urban rail transit demands a deep understanding on the features of track circuit 在此基础上,针对当前应用广泛的基于数字轨道电路的准移动闭塞atc系统进行了重点分析,详细讨论了数字轨道电路的原理、准移动闭塞系统的列控方式等内容,并对准移动闭塞下的最小列车追踪间隔时间进行了理论计算和分析,给出了数字轨道电路长度的推荐值。