HDSL is an
acronym for High bit-rate
Digital Subscriber Line.
It provides
T1 or
E1 connections over two or three
twisted-pair copper lines, respectively. Unlike most other forms of
DSL, HDSL is not a typical consumer service, it's used mostly to replace traditional
T1/
E1 connections, such as connecting
PBXes to
telco offices.
The advantage of HDSL over the
Alternate Mark Inversion line coding scheme traditionally used on T1/E1 lines is that it requires about an order of
magnitude lower
bandwidth to carry the same
traffic.
Source : http://www.dict.org