HDSL - High bit rate Digital Subscriber Line
The earliest variation of DSL. It is used for wideband digital transmission within a business and between the telephone company and a customer. HDSL is symmetrical meaning an equal amount of bandwidth is available in both directions.
A HDSL circuit is made from two modems, one on each end, and two twisted pair copper wires. The line rate is 2.3 Mbps, with a 2 Mbps (E1) payload rate available.