ISDN handles all types of information - voice, data, studio-quality sound, static and moving images. They are all digitised, and transmitted at high speed.

ISDN can handle many devices and many telephone numbers on the same line. Up to eight separate telephones, fax machines or computers can be linked to a single Basic Rate ISDN connection and have different phone numbers assigned to them. (We'll explain Basic Rate in the following pages).

A Basic Rate ISDN line can support up to two calls at the same time. Any combination of voice, fax or PC connections can take place at the same time, through the same ISDN line.

From a digital ISDN telephone you can place a call to an analogue telephone on the PSTN (Public Switched Telephone Network) and vice-versa. Both networks are interconnected by the network carrier in a way similar to the connection between the mobile phone network and the analogue phone network. For the user, it is completely transparent whether he is calling a GSM telephone, a conventional telephone or an ISDN digital telephone.