What does ADSL stand for

Asks Jasmine

A. ADSL stands for Asymmetric Digital Subscriber Line.

Q. What is ADSL

A. ADSL transmits digital information using high bandwidth on existing copper phone lines. It is asymmetric in that it uses most of the channel to transmit downstream to the user and only a small part to receive information from the user and accommodates analogue (voice) and digital signals at the same time. It was specifically designed to cater for the primarily one-way nature of multimedia communication ie the Internet in that large amounts of information flows to the user (via web pages) and a small amount of interactive information is returned (via email for example).

Q. What is the benefit of having an ADSL line installed

A. The main benefit is that it provides an always on connection which benefits the user as you do not have to continually log on and off before and after use. It also cuts out the frustration encountered when you try to log on and all lines are busy, or you are continually knocked off a network. It also enables you to download and send large files very quickly.

Q. Why is my existing connection via a normal telephone line so slow

A. A plain old telephone service (POTS) or traditional phone line was created to transmit voice (or analogue) signals only. If you use a modem to connect to the Internet it decodes the analogue signal and changes it into a digital one to transmit data. It therefore provides a slower connection than voice transmissions that is worsened if lots of people are using a network at the same time.

An ADSL line assumes that data does not have to change into or from analogue and automatically sends digital data. At the same time if you want to use the same line for an analogue (voice) signal (ie your normal teleophone line) the signal can be separated so that you can use your telephone and computer on the same line at the same time.

Q. Is ADSL available in my area

A. You can find this out by contacting your local telephone exchange usually via BT or from a growing number of ISPs eg. Freeserve and NTL. All you have to do is provide your telephone number and they'll let you know.

However, there is a waiting list for a connection with BT (the waiting time was six months in April last year, and has now been reduced to three months). So expect to wait more that three working days for the service!

A report issued by Datamonitor on 3 May 2001 states that potential UK customers will be slow to take-up ADSL until its service benefits are highlighted and they see some real benefit in the service (installation of an ADSL line can cost upwards from 150 not including the monthly always-on fee).

Some companies like Telewest Broadband have launched exclusive websites to showcase their broadband content, available over ADSL lines. This is in a bid to get more customers interested in what broadband can offer - and they have recognised that people want more than just a fast connection for their money. Their Blueyonder service offers exclusive entertainment, music and gaming content via video streaming.

Also, Mac users beware! Before having your ADSL line installed - and you shell out all your money - ensure that your service provider can support your Macintosh, many systems have been designed to support PCs only, which some Mac users have found to their cost. If possible, get it in writing that they can support Macintosh's - because it can be very difficult to have your installation fee refunded later on.

Q. How fast is information transmitted via ADSL

A. It depends on your telephone services provider but it can receive data at rates of up to 6Mbit/s (which in real terms means that you can view video (motion video) in real time with 3D effects). Usually it will provide downstream rates of 2Mbit/s to 512Kbit/s and 128Kbit/s upstream.

Q. When was ADSL introduced

A. It was developed and ready for use in 1998 in the US and has been adopted by other Western countries ever since. In the UK it has been available for home and business use from end-2000, and is gathering real pace at the moment. It will replace ISDN lines in the UK over the next couple of years. In the future, if you have it installed at home or for a small business it is likely to deploy G.Lite (in some areas DSL Lite or Univeral ADSL will be deployed) technology, which is basically an easier to install way of installing an ADSL line. A signal splitter is often needed to split your analogue and digital signal so that both can be used at the same time if this is done remotely (which means you won't require another costly installation from BT or another telephone service provider) it deploys G.Lite, DSL Lite or Universal ADSL and is slightly slower (you won't notice it) than a pure ADSL line.

If you have any other Internet & Technology related questions, please click here

By Karen Anderson