Symmetric Digital Subscriber Line (SDSL) is a Digital Subscriber Line (DSL) variant with E1-like data rates (72 to 2320 kbit/s). It runs over one pair of copper wires, with a maximum range of about 3 kilometers. The main difference between ADSL and SDSL is that SDSL has the same upstream data transfer rate as downstream (symmetrical), whereas ADSL always has smaller upstream bandwidth (asymmetrical). DSL Modem Digital Subscriber Line, or DSL, is a family of technologies that provide a digital connection over the copper wires of the local telephone network. ... In telecommunications, T-carrier is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America and Japan. ... Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. ... Symmetry is a characteristic of geometrical shapes, equations and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ... Symmetry is a characteristic of geometrical shapes, equations and other objects; we say that such an object is symmetric with respect to a given operation if this operation, when applied to the object, does not appear to change it. ...

SDSL was never properly standardised until G.SHDSL was standardised by ITU. SDSL is often confused with G.SHDSL and unfortunately, in Europe G.SHDSL was standardized by ETSI using the name 'SDSL'. This ETSI variant is compatible with the ITU-T G.SHDSL standardized regional variant for Europe. Single-pair high-speed digital subscriber line SHDSL is a telecommunications technology for DSL subscriber lines. ... The International Telecommunication Union (ITU) is an international organization established to standardize and regulate international radio and telecommunications. ... World map showing location of Europe When considered a continent, Europe is the worlds second smallest continent in terms of area, with an area of 10,600,000 km² (4,140,625 square miles), making it larger than Australia only. ... The European Telecommunications Standards Institute (ETSI) is a standardization organization of the telecommunications industry (equipment makers and network operators) in Europe, with worldwide projection. ... The International Telecommunication Union (ITU) is an international organization established to standardize and regulate international radio and telecommunications. ...

Equipment touting SDSL support is usually proprietary equipment which only speaks to SDSL equipment from the same vendor, or to SDSL equipment from other vendors that use the same DSL chipset. Most new installations use G.SHDSL equipment instead of SDSL. A chipset is a group of integrated circuits (chips) that are designed to work together, and are usually marketed as a single product. ...

See also

• ADSL
• ISDN