ADSL (or Asymmetric Digital Subscriber Line, in its full glory) is the most common broadband technology, and involves connecting to the internet down a BT telephone line.

ADSL converts it to a high speed digital line up to 40 times faster than a traditional modem. It is asymmetric because it provides more bandwidth in one direction than the other.

You will need to plug a microfilter into your telephone socket, which is a special sort of splitter that separates your voice call from your broadband data. This normally comes included with your broadband package.