| ADSL is a kind of broadband Internet connection that | | | | screeching noises they made when they were |
| you can get over your existing phone line. When | | | | connecting? That's because they were encoding the |
| people hear about this, they often wonder how on | | | | data they sent over the phone line as sound - all those |
| earth it can be true. Doesn't the phone line need to be | | | | ones and zeros were becoming a series of sounds. It |
| upgraded? How can all that extra data fit through an | | | | was an analogue to digital to analogue conversion at |
| ordinary phone line? Why weren't they doing this years | | | | each end, and was wildly inefficient. |
| ago, when I was still dialling up with my old modem? To | | | | What DSL does is use the unused frequencies of the |
| understand the answers to these questions, it's | | | | phone line (that is, the parts that aren't needed for |
| necessary to learn a little about how ADSL works. | | | | voice signals) to carry digital signals, in the form of |
| ADSL stands for Asymmetric Digital Subscriber Line. | | | | electrical pulses instead of sound - it's a successor to |
| The 'asymmetric' part simply means that you can | | | | ISDN, the expensive business precursor of the |
| download over the line faster than you can upload - | | | | technology. This method is much, much faster than the |
| good for home users, who generally download (get | | | | old analogue way. The unused part of the line isn't that |
| things from the Internet) far more than they upload | | | | big, but DSL splits it up into many smaller pieces and |
| (send things to it). | | | | uses each one separately, allowing multiple 'channels' |
| It's the 'digital' part that is important, however. If you | | | | of data to be sent and received at once. |
| think back to old dial-up modems, remember the | | | | Who said you can't teach an old dog new tricks? |