Broadband

What is Broadband - DSL?

Broadband can be delivered by Digital Subscriber Line (DSL) which is a modem technology that transforms a normal telephone line into a high-speed digital line. DSL enables fast access to the internet whilst allowing telephony services to be used at the same time. DSL provides always-on, always available, access to the Internet at speeds that are 10 to 40 times faster than a standard 56k modem.

Asymmetric DSL (ADSL)

ADSL stands for Asymmetric Digital Subscriber Line. It is asymmetric because the downstream rate (the data you receive from the internet) is much higher than the upstream rate (the data you send to the internet). The downstream rate is a maximum of 512kbit/s whilst the upstream rate is a maximum of 256kbit/s (service providers offer higher rates of up to 2Mbit/s downstream at higher cost). With most ADSL the telephone can still be used at the same time as the broadband, by fitting a microfilter for each phone.

ADSL deployment

ADSL is normally available to premises within 5km of an ADSL-enabled local exchange, but BT recently extended this to 10km for rate adaptive variants.

To find out if you are in range, BT provide a Broadband Availability checker, click here to check your line. Rate-adaption is achieved by reducing the upstream rate to between 64kbit/s and 250kbit/s depending on distance from the exchange. The downstream rate can be reduced to 256kpbs in some cases.

Self-install ADSL modems are now provided by most service providers. They enable end-users to purchase ‘off-the-shelf’ modems and micro-filters, and install it themselves. BT (who own most telephony lines in the UK) do not need to send an engineer to complete the installation. Your chosen service provider will contact BT on your behalf and request BT to connect your line in your local exchange to their ADSL equipment (this can take up to 10 days) and will inform you when your broadband connection is ready to use.

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