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There are many different forms of DSL. Currently only two forms are available in the United Kingdom. These are ADSL ( Asymmetric Digital Subscriber Line ) and RASDL ( Rate Adaptive Digital Subscriber Line ) . Both of these are available in a Wires Only version. DSL is a special telephone line which allows you to access the internet at a much higher speed than your standard 56k modem. The installation of DSL gives you a permanent high-speed digital connection to the Internet. It also has the added advantage of allowing you to make voice calls on a standard telephone at the same time as accessing the Internet. What is the difference between ADSL and RASDL ? RADSL is a newer system than ADSL, it is designed to automatically adjust your upstream bandwidth to allow for a wider downstream frequency band. This means that the connection will be more tolerant towards errors caused by line noise, allowing BT to install RADSL further away from their exchange's than ADSL. The only disadvantage is that this technology is only available at the maximum speed of 512k. What is the Wires Only version ? ( installation without a BT router ) The idea behind Wires Only is that BT will just provide the wire. You have to get your own router and filter. This has many advantages. The first is that you don't need a BT engineer to visit your office, saving you both time and hassle. The second advantage is that you don't have to rent BT's router from them. This means you are saving yourself at least £ 4 a month. There other many other advantages as well including the ability to upgrade your router so that it includes features like security. This is something which is simply not possible using a BT router. Lawyers Online can provide Wires Only along with a preconfigured router. This is a talor made package that is designed to keep your costs down while not forcing you to become a network engineer. Why would I need a Microfilter ? If you have the 'wires only' ADSL service then you will need an ADSL splitter (sometimes called a microfilter) for each phone socket around your office. The splitter separates the ADSL (high frequency) signals from the analogue phone (low frequency) signals. What speeds can ADSL run at ? ADSL is currently available in three speeds, 512k, 1MB and 2MB. These are the maximum download speeds, all upload speeds are at a maximum of 256k. Actual Line speeds vary depending on distance from the exchange and how many users are currently active. What can I do with ADSL? A simple answer to this would be: Anything you already do with your current modem connection, just much faster. However ADSL is not suitable for hosting web servers or live data accessed via the Internet. This is because ADSL is asymmetric (It downloads faster than it uploads) users trying to access from the web will only have access at 256k bandwidth, which is also at a contention ratio of 20:1. If you need to host web servers then you will need a leased line with guaranteed symmetric bandwidth. Is it Secure? A simple answer to this would be: No security is provided by having an ADSL line. To be secure you should invest in a security product (eg. a firewall). Lawyers Online recommend that you use some sort of firewall to protect your network from attack. ADSL is an "always on" service and so open to the Internet as along as your PC's are switched on. Firewall solutions are available on request. What are contention ratios? Contention means that the connection from your local exchange to the ISP is shared by other users. It is quoted as a ratio i.e 50:1 - meaning a maximum of 50 people will be sharing your allocated bandwidth (e.g. 512kbps). In actuallity the number of people sharing bandwidth is more complex. The contention ratio for business use is 20:1, meaning up to 19 other users will share your bandwidth. The cheaper Home user service will be on a ratio of 50:1. What do I need to have ADSL?
What is the Minimum Contract Term? Lawyers Online passes on the minimum contract term imposed on ourselfs by BT. The contact term is different for our different accounts and packages. Our standard minimum contract term is 12 months. If you cancel before the 12 months are up you will have to keep paying, although you aren't receiving any service, until the end of the contact. Some of our ADSL packages have a minimum contract term of 6 months. What about a BT line with a DAC connected? If your line has a DAC ( a DAC's is a device BT use to share a pair of copper wires between two phone lines ) you have to have the DAC removed from the line. The procedure to do this is to apply for your ADSL line, and BT when doing the various checks should spot the DAC's and arrange for the removal of the device. This may delay your order a few days, but once removed shouldnt stop you from having ADSL so long as your line passes the various tests. What about a BT line made of fibre? DSL will only work over copper wiring. If your phone line has any fibre optic cable between you and the exchange you wont be able have DSL services. If BT installed the DSLAM at the point where the fibre optic cable was split out onto individual copper lines it would be possible for BT to provide DSL services. At present though BT are only deploying DSLAM's inside exchanges. What are the tests that BT carry out? BT will carry out tests on:
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