Products


1.
Data Connection & ADSL
2. ADSL Quick Guide
3. ISDN services & benefits
4. Voice over IP explained
5. What is ADSL?

What is ADSL?

ADSL or Asymmetric Digital Subscriber Line technology is a means of transmitting digital information at high bandwidth down existing copper telephone cable. It is permanently 'switched on', unlike normal dial up access and is asymmetric in that it uses most of the available bandwidth downstream. This makes it particularly suitable for applications where customers expect to receive more data than they transmit such as for Web browsing, use of corporate intranets, and reception of digital audio-visual material. The technology also supports analogue connection on the same line, which enables voice or fax calls to be made simultaneously.

What are the key benefits of ADSL for me?
Firstly, the speed ADSL provides - high-speed digital access - e.g. potentially 10 to 40 times faster than today's typical modems. It’s Always On. You will no longer have to waste valuable time obtaining a dial-up connection to your Internet Service Provider or Corporate Intranet It’s Flexible. It does not affect the normal telephone, so you can make and receive telephone calls or faxes whilst you’re online.

What are the key benefits of ADSL based services for Business?
ADSL based services will allow SME's and Corporates to:
* Take full advantage of broadband capabilities.
* Offer innovative services to your end user base.
* Extend the reach of your Intranet to encompass your remote teleworkers and satellite offices.
* Manage and predict your costs with the flat rate charging scheme

How fast is it?
Typical rates for ADSL are shown in the table below. Downstream speed upstream speed Up to 500kbit/s Up to 250kbit/s Up to 1Mbit/s Up to 250kbit/s Up to 2Mbit/s Up to 250kbit/s.  This is between 10 to 40 times faster than today's typical modems.

Who are our ADSL based services aimed at?
Our services are aimed at a wide range of consumers. Corporate business users will be able to provide their teleworkers or satellite offices with remote access to the corporate network, whilst home users will be able to take advantage of the incredible download speeds to view digital media on the Web, such as movies, music and similar bandwidth hungry applications.

What can ADSL be used for?
ADSL's higher potential bandwidth has the potential to enhance access to existing services and applications and stimulate the development of new ones: Internet access The access speeds available with ADSL available make it practical for web sites to carry more multi-media rich information such as embedded video clips, animations and good quality audio - significantly enhancing the online experience Intranet access Fast access to the Intranet makes teleworking an attractive option - which in turn can bring benefits to both the organization and the individual TV based services ADSL can be used to deliver interactive applications to the TV, such as real time video and audio, home shopping and home banking.
Future services
ADSL will be the catalyst for a wealth of new information, education and entertainment services

When will I be able to have ADSL installed?
Broadband is dependent upon BT's roll-out schedule for ADSL serviceability of your geographical area.

How have BT chosen which exchanges get ADSL enabled first?
BT has chosen a number of criteria to establish which exchanges should be provisioned for ADSL first. These included demand for bandwidth and where the early adopters of these services are most likely to be located.

What do I need in order to be ADSL serviceable?
There are a number of factors that will determine whether you will be able to take advantage of ADSL. These include:
- That you are a BT subscriber
- You must have a valid contract for the use of a BT analogue direct exchange line forming part of the BT network over which the ADSL service will be provided
(Note that if you rent your premises, you must have a valid contract for a BT or Calls & Access provided PSTN line.  It is not suitable that the contract be held with your landlord rather than yourself)
- Whether BT has upgraded your telephone exchange to ADSL technology, and whether you are located within a specified distance from the exchange
- That you are aware of the installation procedure and requirements in terms of equipment as well as location
- That there are no incompatible services on your PSTN line
- That you have sufficient mains power sockets for the BT NTE
(Network Terminating Equipment)

Are there any Service Constraints I should be aware of?
The transmission performance of some local loops will mean that it is technically impractical to deliver ADSL service to all end users with a particular serviceable area. BT reserves the right to refuse ADSL installation even if you are situated in a serviceable area.

What services on my line are incompatible with ADSL?
ADSL service is not compatible with these BT services: Subscriber private metering 30k loop Private circuits Red ABC RedCare Meterpulse facility PBX lines It is only possible to provide a single broadband service over a single BT or Calls & Access PSTN exchange line.

How does ADSL work?
ADSL operates over a normal telephone line. This means that there is no need to dig up any roads to replace cable and install it. The ADSL signal is carried by two ADSL modems - one in the end user's premises and one in the local exchange. These ADSL modems are designed to exploit the physical transmission capabilities of the copper line to the maximum extent. The resultant ‘broadband’ medium is used to achieve much higher data rates than were previously possible. Two 'splitters' (filters), one in your premises and one in the BT exchange, separate the telephony signal from the ADSL signal. This means that telephone calls can be made at the same time that data is being sent or received (i.e. a customer can surf the Internet and still make telephone calls concurrently).

Is my fax compatible with an ADSL set-up?
It is not guaranteed that your existing fax machine will work after you have installed ADSL. Please check with the fax machine manufacturer for ADSL compatibility.

Will ADSL affect my normal telephone connection?
You may notice a slight change to how your telephone sounds after you have ADSL installed. This is normal for ADSL lines and is not a fault. Any standard modems operating on your PSTN line (standard telephone, not the ADSL line) may operate at a reduced speed after ADSL installation

Will telephone calls be charged separately?
Yes. Normal telephone rental and call charges will still apply.

Can customers keep an existing telephone number?
Existing BT PSTN numbers will be unaffected; most end users will be able to keep their existing telephone number.

Who is responsible for billing?
You will make payment arrangements with us for your ADSL service. If you have any queries about your ADSL account you should contact us and not BT. The price, billing and payment for your standard BT telephony service will remain unchanged and BT’s responsibility.

Will all BT Select services be supported?
Yes, all Select Services can be supported on the PSTN line, including Call Waiting, Call Return and Caller Display.

Will ADSL affect my burglar alarm or security system?
Installation of ADSL may adversely affect security or burglar alarm systems that use your PSTN telephone line and fail to operate correctly. You should check with your suppliers for compatibility of your system before arranging for ADSL installation.

Which IP services are compatible with ADSL?
The service supports most protocols including Telnet, SMTP, HTTP, FTP, TFTP, VDO, RealAudio, Cu-SeeMe, QUAKE (2.8.0). ADSL will also support instant messaging and communication programs such as NetMeeting, ICQ or Microsoft Messenger. Some of the advanced functions of these programs, such as video conferencing or file sharing, will not operate behind a firewall or Network Address Translation (NAT) without some technical configuration, or possibly not at all. If you have any questions, consult the user Help for the specific program.

What computer equipment do I need?
The equipment required and minimum specification of PC depends upon which installation you are having, USB or Ethernet version. For the ADSL Home and ADSL NetStart USB installation, you will need the following: PC with the minimum specification of: Windows 98 or Windows 2000 operating system USB port (if you are not sure about this, please see your supplier. The ADSL modem uses USB to connect to your PC). 4-speed CD ROM drive 200Mhz Pentium or above 32 Mb RAM or higher Video card/display capable of 800x600, 256 colours SVGA monitor 16 bit sound card 150 MB free hard drive space For the Ethernet multi-user modem/router installation, you will need the following: PC with the minimum specification of: Network Interface Card (10BaseT Ethernet port) TCP/IP communications stack Netscape 4 or IE 4 or above must be loaded onto at least one of the PCs connected to the service. The browser must be JavaScript enabled. Other specifications will depend upon the applications you want to use with your ADSL service and the operating system you are using. For basic Internet browsing this should be at least: Pentium 166Mhz, MMX or above 32Mb RAM or above 150MB available hard disk space SVGA or higher rated monitor Video card/display capable of 800x600, 256 colours Windows 3.11, Win 95 or Win 98 - or, Windows NT or Windows 2000 4-speed CD ROM player 16 bit sound card Mouse or other pointing device If you wish to use Apple MacIntosh on your network, the machine should conform to the following specification: Or a Apple Macintosh with the following is recommended: PowerPC 601 or equivalent 32MB System Memory 2-speed CD ROM player Video driver and display capable of 800 x 600, 256 colours 100MB free space on hard drive OS8.1 or higher Open Transport 1.3 Networking Software 10baseT Network Adapter with an RJ45 connector You will also need appropriate lengths of Ethernet cable to connect your PCs to the ADSL router/hub. Note that a length of 100 meters must not be exceeded between the PC and hub.

Can you tell me more about the line testing and validation?
After initial ordering, BT engineers will make preliminary tests on your line to make sure that you are ADSL serviceable. If the tests conducted on your line show that BT are unable to install ADSL at your location, you will be told the reason for this. Some examples of situations may be line quality, distance from the exchange, incorrect information being supplied upon application etc.

What is the minimum contract period?
There is a 3 month minimum contract period. You should however contact us rather than BT if you have any queries.

If I move premises what will happen to my ADSL connection ?
Your contract with BT and ourselves is for your specific location and subject to a minimum period. This minimum subscription period would remain payable if you move location whether or not your new location is ADSL serviceable. If you require ADSL at the new premises then you should make arrangements for a new installation and your old contract will be replaced by a new one

Who do I report faults to?
You should report faults to us and not BT in the first instance. The only exception to this is if the fault affects only telephony services.

Is it dangerous to be permanently attached to the Internet?
Any computer that is connected using ADSL to the Internet is exposed to the same security risks as a dial-up user, however since ADSL users are typically connected to the network for longer periods of time (always on) this risk is potentially that much greater. You should be aware of the potential of hacking attacks and the precautions that you should take. Please read our security section. Some examples of good security practice are: Turn off your PCs when not in use. Turn off Windows File and Printer Sharing Install a virus checking software product and ensure that it is maintained to the latest version. You should provide a Firewall in the case of a sensitive installation. You should provide encryption of sensitive data.

Can you explain how the contention ratios work?
The USB modem and the Ethernet router solutions have different contention ratios set up by BT, with these values set at 50:1 and 20:1 respectively. This means that for a Home user with a USB modem, the BT connection at the exchange is shared with another 50 users. Whilst some degree of performance loss will be experienced during peak periods, it is generally accepted that few people will be downloading or uploading data all at the exact same time. For the business user it makes sense to go for the 20:1 business version, which will not be subject to so much slowdown at peak periods. The two systems will be able to co-exist on the same 'local loop' due to BT's network tunneling protocols, each connection being given its own port on the exchange terminating equipment (DSLAM.

Do ADSL services work with non-BT PSTN lines?
Currently the Broadband services are only available over a BT PSTN line. A non-BT PSTN variant is being investigated.

What standard does BT's ADSL modem adhere to?
Various forms of ADSL signal modulation are possible but the two more prevalent are: Discrete Multi-Tone (DMT), and Carrier less Amplitude modulation Phase modulation (CAP). DMT uses interleaving to achieve good error performance and has become the international standard. BT evaluated both DMT and CAP modems during their extensive trials throughout 1998 and 1999. However, their commercial ADSL based services will use DMT. Alcatel and Fujitsu will supply these modems.

Will BT be blocking any TCP port numbers? There has been some speculation in the press regarding the supposed prospect of port blocking on the ADSL service. The huge popularity of distributed networking programs such as Napster, Gnutella and iMesh has led to fears of excessive bandwidth consumption. BT have stated that they have no current plans to restrict bandwidth use or block particular ports, although they may review this in the future if the service is adversely affected by flagrant bandwidth abuse.

What about other technologies? What impact will UMTS have on ADSL? Universal Mobile Telecoms Service - UMTS is the called the 3rd generation mobile service. It is a mobile network whereas ADSL runs over a fixed network. So, whilst UMTS will deliver broadband access too, the two technologies are more likely to be complementary rather than head-on competitors.

What is DSL Lite technology compared to ADSL?
DSL Lite/G.Lite is a lower speed, splitter less version of ADSL. It is designed to offer around 1Mbps of capacity downstream, and 120kbps upstream. Because there is no Splitter, it is easier to install but does mean that the end user may experience significant interference between the telephony and ADSL services when they are used at the same time. BT's ADSL based services are based on the full ADSL standard, rather than DSL Lite. BT is involved in the evolution of the standard for DSL Lite but has no immediate plans to launch services based on it.

Disclaimer
Please note that although we endeavour to make sure that the information included in this FAQ is up-to-date and accurate we cannot guarantee that it is exhaustive, nor that changes won’t be made at any time without prior notice.

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