The ADSL broadband service makes use of your existing BT telephone line by splitting the line into two distinct channels - one for voice and the other for the high speed data connection. The high speed data connection uses a higher frequency range not used in normal voice communications.

The ADSL signal is carried by two broadband modems - one in your home / office and the other in the BT telephone exchange.

The main benefit of ADSL is that you can use the line for normal voice communication and high speed / broadband access at the same time - often negating the need for a second line if it were to be used solely for Internet access!

Ultimately ADSL 'squeezes' more capacity out of a the same telephone line without interfering with your normal telephone services.