This ETSI Technical Report (ETR) describes a transmission technique ca lled High bit rate Digital Subscriber Line (HDSL), as a means for the transportation of several types of applications. The ETR defines the r equirements for the individual HDSL transmission system, the transmiss ion performance, the HDSL maintenance requirements and procedures and the mapping of information from the dedicated applications. An individ ual HDSL transceiver system is a two wire bidirectional transceiver fo r metallic wires using the echo cancellation method. Three systems may be utilized, one transporting a bit rate of 784 kbit/s over each of t hree pairs used in parallel, a second with an increased bit rate of 1 168 kbit/s and two pairs in parallel only and a third with a more increased bit rate of 2 320 kbit/s on one pair only. The line code of systems specified in t his ETR is 2B1Q (two Binary one Quaternary). Systems using a CAP (Carr ierless Amplitude/Phase modulation) line code are covered in annex B.