ADSL (Asymmetric Digital Subscriber Line)
Defining ADSL
Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. It does this by utilizing frequencies that are not used by a voice telephone call. A splitter - or microfilter - allows a single telephone connection to be used for both ADSL service and voice calls at the same time. Because phone lines vary in quality and were not originally engineered with DSL in mind, it can generally only be used over short distances, typically less than 3mi (5 km). Also, every ADSL connection speed is still determined by the line length and quality of copper between your premises and local exchange.
ADSL provides much faster access than previous alternatives. Fixed rate ADSL can download data at speeds from 512Kbps to high as 24 Mbps and upload at up to 1 Mb/s. And, because ADSL provides an always on connection you can transfer whenever you want. ADSL is part of the xDSL family, which covers a number of similar yet competing forms of DSL, including SDSL, HDSL, RADSL, and VDSL.
Advantage over ISDN
ADSL is faster, permanently connected, the costs are set and not dependent on usage and you can use an existing BT phone line where as ISDN needs installation of an additional line
What are the benefits of ADSL?
- Speed - A good quality modem can download information at rates of up to 56Kbps. ADSL provides speeds of between 512Kbps and 2Mbps when downloading information onto your computer and 256Kbps when you are sending information out.
- Fixed cost - Depending on the type of contract, ADSL could mean no more anxious days awaiting the next phone bill to see how much you have spent accessing the Internet.
- Permanent connection - ADSL is a permanent "always-on" connection so no dialup is required.
- Flexible - Your existing BT phone line is converted to ADSL but you can still use it for phoning and faxing.