Integrated Services refers to Voice, Image, Video, and other data to be transmitted. Digital refers to the digitally converted/upgraded Terminal Equipment, Local Loops, Trunks, Switching, and Signaling. Network refers to the Worldwide, interoperating communication fabric.
The ISDN standards have been defined by the Consultative Committee on International Telegraph and Telephone (CCITT) also known nowadays as ITU-T, a Telecommunication Standardization Sector of the United Nations’ International Telecommunications Union (ITU).
The ISDN have two levels of service. The Basic Rate Interface
(BRI) which consists of two 64 Kbps B-channels and one 16 Kbps D-channel, Thus
making it enough for the home and small businesses. Primary Rate Interface is
another level of service which consists of 23 B-channels and one 64 Kbps
D-channel in the United States or 30 B-channels and 1 D-channel in Europe,
making it ideal for larger users.
Some of the applications of ISDN are for creating Multiple Channels. To create a connection between every possible device present at home. Another is the Digitizing of Telephone which provides clearer reception for subscribers. Facsimile also have to be digital having a standard of 64KBps fax operation. Analog Fax Machines on the other hand needs to use a modem to digitize them at 64KBps. Video Conferencing and Telemetry are also included in the application of ISDN.
Although ISDN is a great technology-driven service, it does have its exemptions/limitations. Like some of the other technologies available, it needs the help of other technologies to fill in its limitations.
References:
Broadband Telecommunications Handbook, Regis J. Bates
