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The majority of home Internet users have turned to ADSL to connect to the Internet. Most people agree that for the average home user, ADSL is one of the best choices for a broadband connection to the Internet. But even though home users know they need a hub or router of some kind and that ADSL uses their existing telephone line, not many people actually know just how ADSL actually works or, for that matter, what it stands for.

 

ADSL stands for Asymmetric Digital Subscriber Line. The name describes, in a nutshell, just what ADSL is and how it works. The second part of the name, ‘Subscriber Line’, refers to the actual telephone line being used. This is the normal copper telephone lines that people use everyday to make phone calls. Normal telephone calls only use a small part of the frequencies available on copper line. ADSL takes advantage of the remaining frequencies to offer users a broadband connection to the Internet.

 

The ‘Digital’ part of ADSL is rather important. Old dial-up modems converted the digital signals from the computer into sound which was then converted in an analog signal that could be sent across the telephone wires. This analog signal was then converted back into sound and then into digital at the other end. With ADSL, the unused frequencies not being used for voice are used to transmit digital signals via electric pulses not sound.

 

ADSL users must still install a POTS (Plain Old Telephone Service) filter at all points where a voice telephone is used. This is to ensure that the frequencies being used on the telephone line do not interfere with one another. While the voice frequencies are unlikely to have a large effect on the digital frequencies; the digital frequencies may cause white noise on the voice frequencies without a filter installed.

 

The frequency range used by ADSL is so large that it can break the data into little packets and send them along multiple channels. This allows larger amounts of data can be communicated more effectively than just using one or two channels.

 

‘Asynchronous’ refers to the how data is transmitted. With ADSL the download speeds are faster than the upload speeds. This ideal for home users that do not have to upload a lot of data, but who often download a lot of data like pictures, video and sound clips. With standard ADSL the frequencies from 25.875 kHz to 138 kHz are used for uploads and the frequencies from 138 kHz to 1104 kHz are used to downloads. Each of these frequencies is then divided further into smaller channels of 4.3125 kHz called ‘bins’.

 

The ADSL router or hub tests these bins regularly to determine which ones are the fastest for data transmission. Electrical, atmospheric and radio interference can reduce the speeds of certain frequencies, making data transmission more difficult. While downloading or uploading, the router or hub will try to use the faster bins to ensure a faster, more stable connection.

 

ADSL is an effective broadband technology that uses existing copper lines to transmit data via electric pulses over the unused frequencies of the telephone line for fast downloads but slower uploads. For the average home user it is the ideal broadband Internet solution that doesn’t require any expensive installations, just a router or hub and an Internet Service Provider (ISP).

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