A Digital Subscriber Line makes use of the current copper infrastructure to supply broadband services. A Digital Subscriber Line requires two modems, one at the phone companies end and one at the subscribers end. The use of the term modem is not entirely correct because technically a digital subscriber Line modem does not to modulation and demodulation as in the modem that uses the normal telephone network. Digital Subscriber lines also have the added benefit of transmitting
telephone service on the same set of wire as data services. Digital Subscriber Line common in many flavor, and are sometimes referred to as xDSL, the x stands for the specific type.
For years it has been believed that the upper limit for transmitting data on analog phone lines was 56 kb/s. This limit is set the maximum possible bandwidth and no compression. The reason for this limit is that POTS or Plain old Telephone service uses the lower 4 khz only. The limit imposed by the POTS lines does not take advantage of all the bandwidth available on copper, which is on the order of 1 Mhz. the xDSL technologies take advantage of this difference and uses the upper frequencies for data services. Previously this was not possible because of the interference that the data services would cause in the POTS band. Advance in digital signal processing have eliminated the near-end cross talk that results from the use of the upper bandwidth for data. The new DSP technologies allow data and POTS to be transmitted on the same set of copper wires without interfering with each other. DSL technology were initially tested for use with video on demand and interactive television. Lack of a killer application for these services and competition from the cable TV industry in these areas forced the telephone companies to look for a different application for their technologies. With the popularity of the World Wide Web and telecommuting on the rise the DSL technologies moved to providing network and phone services to the home.
In Simple Words :–
Digital Subscriber Line is the technology being used for the Internet access. DSL connects your hone or office to the internet through the same telephone wire that comes form the telephone pole on the street. To use the DSL you will need a DSL modem is also known as router, a network interface card, and a telephone line.
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