The generic designation DSL (Digital Subscriber Line) or xDSL describes a group of digital subscriber line technologies. DSL technologies enable better use of the existing copper network, supporting access services that are more demanding in terms of bandwidth.
Some examples of xDSL technology types follow:
- ADSL (Asymmetric Digital Subscriber Line): Asymmetric broadband transmission technology that enables a high-speed (1.5 to 16 Mbits/s) downstream channel (from the network to the user) and a lower speed (16 Kbits/s to 1,5 Mbit/s) upstream channel (from the user to the network), besides normal telephony service in the low frequency range.
- HDSL (High data rate DSL): Symmetric transmission system that allows transmission of 2 Mbits/s in copper telephone lines over a distance of 3.5 km, without repeater, using at least 2 twisted metallic pair circuit.
- SDSL (Symmetrical Digital Subscriber Line): System for symmetric transmission which enables transmission up to 2.3 Mbit/s, based on a twisted metallic pair circuit. Higher bit-rates and distances are attained using 2 pairs of copper.
- VDSL (Very high bitrate asymmetric Digital Subscriber Line): Evolution of ADSL for short distance data transmission at very high speed. A VDSL connection theoretically enables a maximum downstream channel of 51.84 Mbit/s for 300 metres and an upstream channel of up to 12 Mbit/s.