What is Digital subscriber line?
{{DSL technologies}} {{IPstack}} '''DSL''' (for '''Digital Subscriber Loop''' or '''Digital Subscriber Line''') is a way to transmit [[digital]] data over a [[telephone]] line. Telephone lines only transmit a limited [[spectrum]] of signals (roughly 20 [[Hertz]] to 20,000 Hertz, for voice). This means that the other frequencies can be used to transmit [[Information|data]]. The data is combined or [[multiplexing|multiplexed]] onto the telephone line. At both ends, a [[device]] called a ''Splitter'' (or DSL filter) separates the data part and the telephony part. DSL provides the [[physical layer]], the lowest layer of the [[OSI model]] that is used for understanding how the different parts of a telecommunications network can connect with each other. In this model, [[Asynchronous Transfer Mode|ATM]] or [[Ethernet]] are two communications protocols used as the [[data link layer]] (layer 2) and [[Internet Protocol|IP]] is used at the [[network layer]] (layer 3). While most DSL signals are multiplexed for transmission onto telephone lines, DSL can also be used without a telephony line (or multiplexed onto something else, for example [[Cable TV]]). At the consumer end, a DSL [[modem]] converts the [[signal]]s to be able to travel on the phone line; at the other end, a [[Digital subscriber line access multiplexer|DSLAM]] multiplexes or combines the signals onto the [[internet backbone]] of the provider. Most DSL lines of consumers are asymmetric, meaning that connection speeds or [[bit rate]]s are different in each direction. Asymmetric DSL is abbreviated as ADSL. [[File:ADSL filter.jpg|thumb|left|An ADSL filter]] Typically, the [[download]] speed of consumer DSL services ranges from 256 kilobits per second (kbit/s) to 24,000 kbit/s, depending on DSL technology, line conditions and service level implemented. Typically, upload speed is lower than download speed for Asymmetric Digital Subscriber Line (ADSL) and equal to download speed for the rarer Symmetric Digital Subscriber Line (SDSL). [[File:T-DSL Modem.jpg|thumb