Some Frequently asked questions about DSL:


What is DSL?

Digital Subscriber Line (DSL) refers to several types of advanced modems that enable mega-fast access at speeds 300 times faster than most analog modems. Since DSL works on regular telephone lines (unlike, for example, cable modems) DSL systems are considered a key means of opening the bottleneck in the "last mile" of the existing telephone infrastructure, as telephone companies seek cost-effective ways of providing much higher speed to their customers.


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 What Can DSL Be Used For?

DSL is basically a high speed data "pipe" that can be used to transmit any high speed data application, such as video conferencing, fast Internet access, interactive multimedia, on-line home banking, remote office or remote LAN applications. For example, an advertising agency might use a DSL modem in order to send heavy graphic files back and forth for client approvals. They could then submit the print advertisement to the publication in the same way, in a matter of seconds. Another application is known as telecommuting, or work-from-home. An employee with a DSL modem at home will be able to be connect at nearly LAN speeds to their office network, using their regular telephone linewith POTS (plain old telephone service) remaining available for telephone calls, faxes, and so on.

How is DSL Installed?

In order to install DSL, you must have access to the copper infrastructure. This generally refers to telecom operators (PTT's) and in some countries, Internet Service Providers. DSL Modem transceivers must be installed at both ends of the copper line -- one transceiver is placed at the customer premises, and another at the telephone company Central Office (CO) building (or curb cabinet in certain cases).

Unlike previous copper line technologies, the DSL system when installed, does not need manual adjustment. The DSL modem automatically analyzes the line and adapts itself to start up the link within seconds. This process continues once the link is started, as the modem compensates for ongoing changes (such as those due to temperature). The modems contain advanced digital signal processing (DSP) algorithms that produce mathematical models of the distortions caused by the line and produce automatic corrections, so that data is passed (in both directions) on the line. There is usually a performance trade-off; the faster the data rate on the line, the shorter the transmission distance. Other factors that affect range are the gauge (thickness) of the cable, and the amount of interfering noise present.

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