The main digital subscriber loop (xDSL) technologies over one pair of copper wire and some of their technical characteristics and applications are:
Asymmetric DSL (ADSL) - used for fast internet access
Symmetric DSL, (SDSL) and High-speed symmetric DSL (HDSL) - used for 2 Mbits leased lines
Very high-speed DSL (VDSL) - used for high capacity leased line and broadband services ...
