Asymmetric digital subscriber lineÂ (ADSL) is a type ofÂ digital subscriber lineÂ (DSL) technology, a data communications technology that enables faster data transmission overÂ copperÂ telephone linesÂ than a conventionalÂ voicebandÂ modemÂ can provide. It does this by utilizing frequencies that are not used by a voiceÂ telephone call. A MicroÂ filter, allows a single telephone connection to be used for both ADSL service and voice calls at the same time. ADSL can generally only be distributed over short distances from theÂ telephone exchangeÂ (theÂ last mile), typically less than 4 kilometres (2Â mi),Â but has been known to exceed 8 kilometres (5Â mi) if the originally laidÂ wire gaugeÂ allows for further distribution.
At the telephone exchange the line generally terminates at aÂ digital subscriber line access multiplexerÂ (DSLAM) where another frequency splitter separates the voice bandÂ signalÂ for the conventionalÂ phone network. Data carried by the ADSL is routed over Direct Telecom’sÂ data network and eventually reaches a conventionalÂ Internet ProtocolÂ network.
In Spain, the attainable speed of the ADSL connection can vary very much from one street to another and largely depends on the distance from the exchange, the quality of the copper wire and the contention ratio’s of the DSLAM that the customer is connected to.