Asymmetric Digital Subscriber Line (ADSL)

Asymmetric Digital Subscriber Line is a form of DSL, a data communications technology that enables transmission of information at high bandwidths over existing twisted-pair copper telephone lines to homes and businesses.

ADSL is asymmetric in that it uses most of the channel to transfer data downstream to the user and only a small part to receive information from the user. ADSL can achieve downstream data rates of 8 Mbit/s within 1.5 km (5000 ft) of the DSLAM equipped central office or remote terminal and usually start at 256 kbit/s. Upstream rates start at 64 kbit/s and and typically reach 256 kbit/s but can go as high as 1024 kbit/s.

ADSL also supports analog (voice) communication over the same line.

ADSL2 is a new technology that provides higher downstream rates of up to 12 Mbit/s for spans of less than 2.5 kilometers (8000 feet). ADSL2+, boosts these rates to up to 25 Mbit/s for spans of less than 1.5 kilometers (5000 feet).

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