In this paper emergent background of HDSL tech- nology is analysed. Two line transmission codes,2B1Q and CAP used in HDSL are discussed in detail . Fi -nally the major feature,advantage and its spplications of HDSI .

• 本文分析了HDSL技术产生的背景，详细讨论了应用于HDSL中的两种线路传输码：2B1Q和CAP，最后，阐述了HDSL的主要性能、优点及其应用。