This ETR defines the HDSL technique providing transparent capacity of 748 kbit/s over an expected range of 2,75 km with 0,4 mm wires and 3,6 6 km with 0,5 mm or about 1 Mbit/s over one pair of the existing coppe r local line network. It can be used to realise ISDN primary rate acce ss digital section given in ETS 300 233. HDSL allows an economical imp lementation of primary rate over 3 or 2 pairs (compaired to 2 pairs fo r the traditional 2048 kbit/s transmission technique) over more than d ouble the range without a regenerator. Will support the penetration of ISDN with existing network structures and technology. The work will define application scenarios, identify implementations o n the V3 and user-network interface (ETS 300 011), multiplex technique for splitting and recombining 2048 kbit/s to/from HDSL. It requires a maintenance concepts to be identified and taken into account in the m ultiplexer specifications. HDSL may be used for other types of access with lower bit rates. The n eed for this is to be identified and the general concept is to be esta blished by NA.