Rather than introducing a new technology into the fray, DSL uses existing technology in a newer, better way. Essentially, DSL technology allows ordinary copper telephone wires to translate analog signals into digital ones. DSL mines more bandwidth from regular copper telephone wires than what is normally used for POTS (plain old telephone service). DSL modems use digital coding techniques to squeeze up to 99% more capacity out of a phone line without interfering with your regular phone services.

Types of DSL

Asymmetric Digital Subscriber Line (ADSL) is a form of DSL technology that is best suited for the residential user. This service transmits data faster in one direction (downstream to the user) than the other (upstream out to the Internet). It enables Internet users to rapidly download large files and other resources from the web. With ADSL, the upstream and downstream bandwidth is uneven. This is due in part to the limitations of the telephone cabling system and the typical Internet usage pattern, in which most data flows to the user. Downstream speeds generally range from 1.5 Mbps to 9 Mbps while slower upload speeds typically fall in the range of 64 Kbps to 1.5 Mbps.
High Bit-rate Digital Subscriber Line (HDSL) is often the choice for businesses over more costly T1/E1 dedicated access solutions and offers a transmission range up to 12,000 feet. HDSL is the oldest variation of DSL to be widely used within a corporate site and between the telephone company and a customer. Unlike ADSL, HDSL is symmetrical so an equal amount of bandwidth is available for data traveling to or from the user. HDSL technology provides a maximum bandwidth of 1.5 Mbps per second in each direction over two phone lines, or 2 bps per second over three phone lines. HDSL is capable of carrying as much data on conventional telephone twisted-pair wires as can be carried on a T1 line.
ISDN DSL (IDSL) This DSL technology boasts symmetric speeds up to 144 Kbps capacity. However, you can't upgrade beyond the 144 Kbps. The main benefit if IDSL is that it has a much further range from the CO than other forms of DSL.
Symmetrical Digital Subscriber Line (SDSL) offers the same high quality performance whether you are downloading OR uploading data at speeds available from 144 Kbps to 1.5 Mbps. The symmetrical aspect of SDSL makes it one of the best connectivity options available to meet the high demand, two-way traffic needs of businesses. Its high speeds allow you to utilize high-end emerging Internet applications.
Very high data rate DSL (VDSL), also known as Broadband Digital Subscriber Line (BDSL) is the most recent DSL technology that promises much higher data rates. Like SDSL, these exceptional speeds are constrained by distance, with maximum speeds achieved in distances up to 1,000 feet. Like ADSL, VDSL is asymmetric. VDSL can achieve speeds from 1.5 - 2.3 Mbps upstream and from 13 - 52 Mbps downstream.

Benefits of DSL

The key advantage of DSL over modem is speed. The use of DSL technology in your business will enable secure, business-quality connections at affordable prices, and can attract and retain Internet-savvy employees because of its cutting-edge capabilities. With DSL there is no dial-up, waiting or dropped connections, so that the user is able to talk on the phone and still be connected to and use the Internet. One of the most readily rewarding advantages of DSL is that it's always on. By transmitting on existing telephone lines, DSL saves both money and time by simply reusing copper telephone wires that are already in place, thus eliminating the need for installation of a fiber optic cable.

Besides the attractiveness of its speedy access and low cost of installation, there are a myriad of additional benefits to incorporating DSL technologies into your business. DSL can:

Handle large file transfers. DSL is capable of storing and manipulating large amounts of information without loss of connection, allowing the user to zip through online research more productively with fast file transfers.
Enable multiple workers on a network (or LAN-large area network) to connect to a single DSL.
Speed up product development by using the Internet for e-mail, engineering research, market research and collaborative activities.
Carry multimedia, voice & video. DSL can broadcast and receive streaming video/audio, flash animations and allow users to download huge amounts of media without loss of connection.
Facilitate telecommuting with Virtual Private Networking (VPN). VPN telecommuters appear as if they are inside a company's network, gaining access to internal resources and databases.
Allow users to download software and documents from the web 30 times faster than a 56K modem.