ADSL (Asymmetric Digital Subscriber Line): This is a broadband technology that allows high-speed data transmission over existing, ordinary telephone lines. It's usually used as a very high-speed Internet access technology. Eircom i-stream is the brand name of Eircom's ADSL product range. ESAT is offering ADSL in Limerick.

Broadband: This is a communications medium that can carry a wide range of signal frequencies, typically from audio up to video frequencies. In telecoms, the significance of a broadband system is that it can carry television and video-conferencing data as well as voice calls. From an internet-access viewpoint, it means very high speed, very high functionality and the convergence of technologies.

ADSL provides speeds of up to 512 kbps (kilobits per second - see below). The service is distance-sensitive. Typically, customers need to be within two to two-and-a- half kilometres of an ADSL- equipped exchange to receive the service.

ISDN: ISDN provides internet access at speeds of up to 64 kbps on one channel or 128 kbps if both channels are combined. ISDN is less distance-sensitive than ADSL and can be provided up to six kilometres away. ISDN has been commercially available in Ireland for some time. A substantial number of exchanges have ISDN capability. This service also provides voice functionality, while ADSL does not.

Kilobits, Megabits and Gigabits: These are measures of data capacity used to indicate online speed. A kilobit, often abbreviated to kb, is 1,024 bits of data. Megabit (1,048,576 bits) is the unit used when specifying the data capacity of a digital communication link or computer network. A gigabit is roughly 1,000 times a megabit.

These are not to be confused with kilobytes, megabytes and gigabytes, which are measures of computer memory capacity.

Narrowband: Wireless communications systems that employ a large number of channels, each covering a very small range of frequencies.