One of the most significant changes in the way we use the Internet happened with the introduction of ADSL (Asymmetric Digital Subscriber Line). Previously users mostly dialed ino an ISP using some kind of modem or terminal adapter, and were charged for the time spent connected through telephone charges. Moreover, the data transfer rate was severely limited, to around 43Kbps (up to 56Kbps with compression) per telephone line. With technologies such as ISDN, this bandwidth could be increased by using cleaner digital signals and by bunching lines together (e.g. ISDN6 uses six connections to give around 400Kbps), but this still did not represent a significant improvement in bandwidth. This was mainly due to the physical limitations of existing telephone lines--the costs of installing digital fibre-optic lines into every home was prohibitive.

However, the technology called ADSL (Asymmetric Digital Subscriber Line) provides a permanent, high-bandwidth connection over existing copper cable (phone lines). It works by using a much higher frequency signal--which means it can also carry voice signals at the same time--and by using this higher frequency primarily in one direction. A result of this is that the bandwidth in one direction (usually into the home), which is ideal for client-server applications such as web and streamed audio/video.

The fact that this type of connection is permanent and always connected opens up many opportunities. Information services will be the biggest gain, as using the Internet to book airline tickets or check travel news will not need a lengthy connection procedure. In fact, with the set-top boxes that are just becoming available, the Internet can be as easy and fast as switching on the TV.