Only eight years ago in 2000, most of us who connected to the internet at home did so with a dial-up modem that hogged the phone line and made funny noises more often than the average teenager. These days we nearly all do our surfing, emailing and Facebooking at whizzy broadband speeds, but what exactly is broadband, and how does it work?

When people talk of broadband, they're generally just talking about a fast connection to the internet. In the UK, that normally means an ADSL connection over your BT phone line, or a cable connection over a different set of wires into your home. No matter how you get broadband, it's likely to be always-on, so you can surf the internet whenever you want to without paying additional call charges.

Of course, businesses need an internet connection too. Broadband is ideal for home workers and small companies, but larger firms pay much more for even faster connections to the internet. Although these are technically broadband connections too, most people use ""broadband"" just to describe ADSL or cable modem access for home users and small businesses.

Broadband basics

BT broadband packages all use ADSL, which works over a standard BT phone line. So, if connecting to the internet used to involve a phone call and a modem that squealed, how come there's none of that nonsense now? The answer is in the frequencies - bear with us, it's more interesting than it sounds.

Imagine you're listening to a CD that just contains a person talking. No matter how high pitched their voice - in fact, even if they'd been inhaling helium gas - the CD could reproduce much higher notes than a human voice contains. Without other higher-pitched sounds in the recording, a lot of the disc's potential isn't being used.

It's the same with a phone line. You only need a small band of frequencies to reproduce the sound of a human voice, but even a humble copper cable can carry much higher-pitched sounds. Given that we're not using them when we talk, couldn't those higher frequencies be used for something else? You've guessed it - that's how ADSL connections carry information.

You might be wondering why your phone calls aren't drowned out by the noise of all this data, but there's a simple solution. If you've got ADSL, every phone in the house is plugged into a tiny microfilter (sometimes called a splitter). This separates the lower frequencies used for speech from the higher ones used for data, sending speech to the phone and data to your ADSL modem or modem/router.

Go the distance

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