communications, protocol (HDSL) A form of DigitalSubscriber 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.