本技术报告介绍了对双向高比特率数字用户线（HDSL）可行性和可取性的调查结果，HDSL在外环路设备中的双绞线对上运行，有效负载容量大大大于ISDN基本接入DSL。该报告描述了一种HDSL系统，该系统可以提供T1中继线路的替代方案，以1.544 Mb/s的名义速率传输基于DS1的服务。该报告讨论了ANSI T1的HDSL系统支持。403-1988和ANSI T1。408-1990接口标准。

This Technical Report presents the results of an investigation into the feasibility and advisability of bi-directional high-bit-rate digital subscriber lines (HDSL) that operate over twisted wire pairs in the outside loop plant with a payload capacity substantially greater than ISDN Basic Access DSLs. The Report describes an HDSL system that could provide an alternative to T1 repeatered lines to transport DS1-based services with a nominal rate of 1.544 Mb/s. The Report discusses HDSL system support of the ANSI T1.403-1988 and ANSI T1.408-1990 interface standards.