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ADSL Beginners Guide: Summary

Page: Connectors & Wiring Diagrams

What is ADSL?

ADSL ("Asymmetric Digital Subscriber Line") is a type of DSL. It works by splitting your existing telephone line signal into two, one for voice and the other for data. ADSL technology can work at up to 8Mbps download. The most popular services in the UK at the moment are running at speeds of 512Kbps (approx. 9 times faster than a modem), although speeds of up to 2Mbps can be obtained. Upload speeds are 256Kbps on all products and hence this is why it is "asymmetric", because the download speed is different to the upload speed.

How does ADSL operate in the UK?

The majority of services are available through a broad range of ISPs who are reselling products from network operators such as British Telecommunications ("BT Wholesale") and Kingston Communications. It is the responsibility of the network operator to deliver your data (whether it be transmitted using a standard modem, ADSL or some other means) to and from your ISP of choice. It is a common misconception that "BT Openworld" is the only source of DSL service - in fact, "BT Openworld" is just one of many ISPs competing for your business.

What are the advantages and disadvantages of ADSL?

A non-exhaustive list is as follows:


  • High speed "always on" connection
  • Fixed monthly cost
  • Great value for money
  • Competitive modem & router prices


  • Not available to everybody
  • Contended service could result in variable speeds depending upon time of day
  • Possible teething troubles for new or inexperienced customers.

What do I need to get online?

BT Telephone Line

Also, it has to be within 3.5 to 5.5 kilometres of an ADSL enabled exchange (click here to check). Your line must pass a number of tests before installation can go ahead. Kingston Communications customers may also be able to receive ADSL without the need for a BT telephone line.

An ADSL Modem or Router

Most ISPs will supply you with a modem or router either free of charge or at additional cost. A number of online retailers are also competing to sell you their products. Connection equipment can be broken down into 3 basic categories:


The cheapest way to get online with prices below £40. Requires knowledge of how to install into your computer, and is frequently referred to as an "internal" device. PCI modems deliver the best response times (gamers take note!) but also consume CPU cycles to operate.


The easiest way to get online with prices averaging around the £60 mark. Just pop in the CD, install the drivers and plug in the modem. The majority of home users chose USB modems to get online.

Ethernet/Wireless Router

A standalone device which maintains the connection to the Internet for you. Most routers have an Ethernet connection to your local area network and act as a gateway, DNS, DHCP and firewall service. Computer enthusiasts or businesses can use a router to connect multiple computers to the Internet without the need for connection sharing software such as Microsoft Internet Connection Sharing (ICS).

Sample photographs shown - actual manufacturer products vary in features and design. For further information about how to connect up your modem or router, see our connections page.

A Micro-Filter for each Phone Socket

A micro-filter is designed to plug into your phone socket (similar to a standard splitter used to connect multiple telephones). Its purpose is to separate voice from data and must be connected to each phone socket in your house. If you do not have a telephone, or any device which uses the phone line, a micro-filter is not required. Most ISPs and retailers sell micro filters.

All pictures for illustration purposes only.
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