from
The Free On-line Dictionary of Computing (8 July 2008)
High bit-rate Digital Subscriber Line
HDSL
<communications, protocol> (HDSL) A form of {Digital
Subscriber Line}, providing {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.
(1998-05-18)