About DSL (Digital Subscriber Line)

What is DSL?

DSL or Digital Subscriber Line in full is is a family of technologies group under the term DSL or xDSL, which provides digital data transmission over the wires of a local telephone network.

Like dial-up service, DSL uses existing copper pair phone line wiring in conjunction with special hardware on the switch and user ends of the line. This special hardware allows for a continuous digital connection over the phone lines.

As compared to a dialup connection, where a modem is used to connect to the Internet over the phone lines, DSL is always on. There is no need to dial in or disconnect. And DSL is generally much faster than a dialup connection which is limited to 56k.

The DSL modem connects to the telephone wall jack and computer. The device acts as a modulator, translating the computers digital signals into voltage sent across the telephone lines to a central hub known as a
Digital Subscriber Line Access Multiplier (DSLAM, or dee-slam). In lay terms the DSLAM acts as a switchboard for local DSL clients, routing requests and responses between each clients computer address and the Internet.

Since the connection is digital, DSL technology doesn’t have a digital-to-analog conversion like traditional modems. It eludes voice audio spectrum frequency boundaries because it can use frequencies above the voice audio spectrum. This means you can use your phone while maintaining your
Internet connection.

These different frequencies allow DSL to encode more data, and allow Internet
connection speeds of up to 50 times faster than standard modems, and up to 12 times faster than an
ISDN connection. Additionally, since
DSL is not a bus technology, it offers more consistent bandwidth than cable modems in which multiple users share very high bandwidth media. However, distance limitations can affect the transmission rates or can be too great, rendering DSL infeasible. Also, the condition of your existing wiring can affect transmission rates.

The most commonly available DSL technology is

ADSL, or asymmetric DSL. It is asymmetric in that it is designed to accommodate typical consumer Internet use, with much more data flowing toward the user (multimedia and text) than from the user (mostly keystrokes and mouse behavior). The downstream rate (receiving rate) varies from 1.5 to 9Mbps; the upstream rate (sending rate) varies from 16 to 640Kbps. These speeds depend greatly on the distance to the telephone company’s central office.