Unlike dial-up, which uses the phone line to make a connection, ADSL works alongside the frequencies used for voice telephone calling and allows you to continue to make phone calls whilst using the Internet. It also enables faster data transmission through a single connection and allows users to download data and make voice calls at the same time.

The flow of data is grater in one direction than it is in the other - hence the name 'asymmetric'. Download speeds are far greater than upload speeds.

ADSL broadband is therefore more suited to passive Internet use with more need for download traffic than upload.