scope:

The recommendations contained in Technical Report apply to systems that transmit signals over twisted copper cable pairs to provide access to digital telecommunications services. These systems consist of transceiver equipment connected by one or more cable pairs (See Figure1). Transmission between the two transceivers uses digital signals on the cable pairs. The signals may be either two-way on any one cable pair. The transceivers include digital signal processing and may interface to other parts of the telecommunications network via standard interfaces not described in this report. At the external interfaces of these systems, the communication is two-way; bit streams are sent into the transceiver from external sources, and simultaneously, bit streams are sent from the transceiver to external points. The external interfaces may need one or more pairs of wires to handle these bit streams.

While the description of the scope of the project in the previous paragraph is very general, this document is aimed only at high-bit-rate digital subscriber line (HDSL) systems that transport directional digital signals at the nominal rate of 1.544 Mb/s. An option is included to transport half (768 kb/s) of a DS1 payload while still using full 1.544 Mb/s interfaces. This Technical Report discusses HDSL system support of the ANSI T1.403-1988 and ANSI T1.408-1990 interface standards.

This Technical Report does not cover unidirectional transport of 1.5 Mb/s (or higher rate) signals as proposed for Asymmetric Digital Sub-scriber Line (ADSL). The T1E1.4 Working Group is studying ADSL systems.

Purpose

This Technical Report expresses the commonality of understanding developed in the Technical Sub-committee in the process of exploring the technical aspects of the HDSL technology. Meeting the recommendations expressed herein is voluntary. Meeting the recommendations will assure that compliant equipment meets basic functional and performance requirements. Interworking of equipment made by different vendors is desirable, but beyond the scope of this Report.

This report uses forms of the terms "should"", "objective" and "recommends" to indicate the aspects of HDSL systems that are proposed for possible implementation as results of the study project.