What is Dsl?

By: Joseph Brochin
One of the most cost effective high-speed Internet connections is DSL (Digital Subscriber Line). (Asymmetric Digital Subscriber Line) are the most prominent.There are different types of DSL. SDSL (Single in-line Digital Subscriber line a.k.a Symmetric DSL) and ADSL ADSL is the most widely used in residential services and can be a cost effective solution for small businesses depending on their Internet access requirements. ADSL allows for a faster download than upload speed from the ISP. As most users typically download more than upload. ADSL also allows one to use the phone for voice conversations at the same time. SDSL allows for equal download and upload speed. SDSL is mostly used in small businesses that require the transfer of larger files and uploading of information to remote hosts and servers. No matter which type is used DSL works off the same basic principles. DSL uses POTS (Plain Old Telephone) lines already installed on the premises to transfer data. These POTS lines do not use near the capacity they are able to carry when carrying voice conversations. DSL uses this excess capacity to carry data to and from the Internet without disturbing analog phone conversations.

There are two different standards used for ADSL. One is the official ANSI standard called DMTCAP (Discrete Multi-Tone) and is the standard used on most installs today. The other standard is (Carrier less Amplitude/Phase), which was used on earlier installations and is sometimes still used today. To make a long explanation short, CAP standard divides the DSL signal on the telephone line into three distinct bands: Voice, Upload, and Download. DMT standard basically divides the POTS lines into 247 separate channels and passes your voice and data over the 247 separate channels. DMT is much more complex than this explanation lets on, but it is the simplest way to explain it that I know. That being said DMT is much more difficult to implement than CAP. To end this article we will talk about the advantages and disadvantages of DSL. Advantages: 1.) With DSL you can leave your Internet connection open and still use the phone line for voice calls. 2.) DSL speed is much higher than regular dial-up modems. 3.) Doesn't necessarily require new wiring; it can use the phone line you already have. 4.) The company offering DSL usually offers the modem at no extra charge as part of the installation. Disadvantages: 1.) The DSL connection works better when you are closer the Central Office. 2.) The DSL connection is faster for receiving data than it is for sending. 3.) DSL service is not available everywhere.

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