Integrated digital telecommunications and long-distance transmission network: digital network for data, text, language, and image transmission via a telephone cable. A digital connection consists of a 16 kbit/s control channel ['D' channel] and two 64 kbit/s bearer channels ['B' channels]. Such a basic connection allows you to use two services at the same time, e. g. telephone and fax.There exist a great variety of national ISDN protocol variants which are not compatible with each other. Since 1993, Europe has started the conversion to a uniform ISDN protocol (Euro-ISDN).
