What is Digital Subscriber Line (DSL)?

DSL stands for digital subscriber line, a somewhat nondescript name for an exciting technology.

The “D” is historical since the original form of DSL was a digital service. (A DSL line is not a digital line, rather, it is the same analog telephone line you have now. DSL is instead a service provided over your existing copper telephone line, two thin wires called twisted pair. Electronics installed at your house and at the nearest telephone switch enable DSL. In other words, it's the technology at each end of the wire that makes DSL go, not the line itself.)

The “S” or subscriber refers to you or your company. You “subscribe to” or rent the DSL line from a telecommunications service provider.

“L” (line) means that this is an outside line (also called a circuit) that comes into your premises on a telephone cable from a telecommunications service provider. This is the same type of telephone cable used for your everyday telephone service.

DSL is a technology that uses your existing analog copper phone line for high-speed Internet by using a digital frequency that's out of our hearing range. Because of this you can have high speed DSL on the same phone line you use to talk on. In fact, you can talk on the phone while using the Internet.

DSL turns your existing phone line into a three-channel data delivery system. One channel transmits voice and fax services, regardless of whether you are accessing the Internet. The remaining downstream and upstream channels carry information to and from the Internet. There are modems at each end of the phone line. One modem is in your location, while the other is in the telephone company central office. Working together, the modems provide a dedicated connection that avoids the need to dial-up for access. The modem in the telephone central office points your Internet traffic to the DSL network and on to the Internet. You just click on the desktop browser icon to get online!

A point to note in DSL technology, whatever the type, is that there’s a trade-off between speed and distance. That is, the more the distance between your premises and those of the service provider, the lower the speed you’re likely to get. So, DSL works best if you’re closer to the premises of your service provider.