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xDSL - Asymmetric DSL (ADSL) - It is called 'asymmetric' because the download speed is greater than the upload speed. ADSL works this way because most Internet users download much more information than they upload. - High bit-rate DSL (HDSL) - Providing transfer rates comparable to a T1 line, HDSL receives and sends data at the same speed, but it requires two lines that are separate from your normal phone line. - Symmetric DSL (SDSL) - Like HDSL, this version receives and sends data at the same speed. While SDSL also requires a separate line from your phone, it uses only a single line instead of the two used by HDSL. - Very high bit-rate DSL (VDSL) - An extremely fast connection, VDSL is asymmetric, but only works over a short distance using standard copper phone wiring. DSL Type Max. Send Speed Max. Receive Speed Max. Distance Lines Required Phone Support ADSL 800 Kbps 8 Mbps 18,000 ft (5,500 m) 1 Yes HDSL 1.54 Mbps 1.54 Mbps 12,000 ft (3,650 m) 2 No SDSL 2.3 Mbps 2.3 Mbps 22,000 ft (6,700 m) 1 No VDSL 16 Mbps 52 Mbps 4,000 ft (1,200 m) 1 Yes - Voice-over DSL (VoDSL) - A type of IP telephony, VoDSL allows multiple phone lines to be combined into a single phone line that also includes data-transmission capabilities.