Describes a transmission technique called High bit-rate Digital Subscriber Line (HDSL), as a means for the transportation of several types of applications. It defines the requirements for the individual HDSL transmission system, the transmission performance, the HDSL maintenance requirements and procedures and the mapping of information from the dedicated applications. This work item studies the problems involved in combining the transmission of ISDN-BA (or POTS) and 2048 kbit/s data transmission over HDSL transmission systems.