Integrated Services Digital Network (ISDN)

It is a telephone network depending on fibre optics and microwave links to carry computer-controlled digitized messaging signals originating from a variety of sources and equipment. Such signals can transmit voice, video, computer data, electronic mail and fax, separately or simultaneously. The only limitations are the different operating methods and protocols in use locally by companies and/or countries, with the ultimate being the possibility of sending all types of messages, however generated, from anywhere to anywhere else in the world, speedily and without complications.

The phone network exists, and the digitizing and transmission of a variety of messaging forms controlled by computer is already taking place. ISDN2 has been introduced to address the problems as they relate to small businesses and branch offices.