Digital connections

ISDN

An ISDN (Integrated Services Digital Network) capable phone line can provide connection speeds of up to 64Kbps (single channel) or 128Kbps (dual channel) using a terminal adapter often referred to as an ISDN modemmodem: a piece of hardware that connects a computer to the Internet. The terminal adaptor removes the need to convert digitaldigital: data measured at discrete intervals, eg a digital watch typically moves from displaying one second to the next without displaying the values in-between signals to analogue signals before they’re sent down the telephone line, this results in a more reliable Internet connectionInternet connection: a computer's or another internet-enabled device's connection to the Internet.

ADSL

ADSL (Asymmetric Digital Subscriber Line) provides connection speeds of up to 24Mbpsmegabits per second (Mbps): a measurement of data transfer speed and uses a telephone line to receive and transmit datadata: information without context, eg a list of students with numbers beside their names is data, when it's made clear that those numbers represent their placing in a 100 metre race, the data becomes information.

A digital Internet connection

The speed that data can be transferred is dependent on a number of factors:

• Phone lines were designed to carry voice signals - not data. Signal quality can vary between lines and whilst it doesn’t affect voice signals, it does affect data transmissions.
• The distance between your house and the telephone exchangetelephone exchange: a system of electronic components that connects telephone calls and has been adapted and expanded to facilitate connections to the Internet too has an effect on the speed at which data is transferred. A distance of 4Km is considered the limit for ADSL technology, beyond which it may not work.

An ADSL modem/routerrouter: a device for connecting computers and other network capable devices together to form a network is needed for broadbandbroadband: high speed Internet access Internet access over ADSL. This is usually provided by your ISPInternet Service Provider (ISP): Internet Service Provider - needed in order to access the Internet, they also provide services such as web space and email.

Phone calls can still be made whilst connected.

Cable

Cable companies do not use traditional telephone lines to provide broadband Internet access. They have their own networknetwork: a group of interconnected computers, a combination of co-axial copper cable and fibre optic cablefibre optic cable: cable that carries data transmitted as light.

With their purposefully built infrastructure cable companies are able to provide speeds of up to 50Mbps - considerably faster than the highest available ADSL speed (24Mbps).

A cable modem/router is needed for broadband Internet access over cable. This is usually provided by your ISP.

The making and receiving of phone calls is not affected because the telephone line is not used.