Chapter 10:                   INTEGRATED SERVICES DIGITAL NETWORK (ISDN)

             INTEGRATED SERVICES DIGITAL NETWORK (ISDN)  is a set of communication standards for simultaneous digital transmission of voice, video, data and other network services over the traditional circuits of the public switched telephone network. It was first defined in 1988 in the CCITT red book. Prior to ISDN, the telephone system was viewed as away to transfort voice, with some special services available for data. The key feature of ISDN is that it integrates speech and data o the same lines, adding features that were not able I the classic telephone system. There are several kinds of access interfaces to ISDN defined as Basic Rate Interface (BRI), Primary Rate Interface (PRI), AND Broadband ISDN (B-ISDN).

             ISDN is a circuit-switched telephone network system, which also provides access to packet switch network, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in potentially better voice quality than an analog phone provide. It offers circuit-switched connections (for either voice or data), and packet switched connections (for data),I in increments of 64 kilobit/s. A major market application for ISDN in some countries internet access, were ISDN typically provides a maximum 128 kilobit/s in both upstream and downstream direction. Channel bonding can achieve a greater data rate; typically the ISDN B-channel of 3 or 4 BRIs (6 to 8 64 kbit/s channels) are bonded.

             Integrated services refers to ISDN's ability to deliver at minimum two simultaneous connections in any combination of data, voice, video, and fax, over a single line. Multiple devices can be attached to the line, and used as needed.There were about 1500 Telcos in the USA. AT&T,GTE and IIT owned almost of the important ones covering the large population centers only on canada that the telephone company was solely owned by the  provincial government,through they were also has many small independent Telcos in some outlying areas.As the CCITT changed thier name to ITU-T,it has become a UN treaty organization,as such,each of the country was intitled to send representatives to any committee meeting.Representatives comes from the government-run PTT Monopoly determining who will represent each country's interest at ITU-T,historical actions & compositions are discussed with the CCITT sane with the currents actions with ITU-T.

                  ISDN (Integrated Services Digital Network) is a set of CCITT/ITU standards for digital transmission over ordinary telephone copper wire as well as over other media. Home and business users who install an ISDN adapter (in a place of a telephone modem) receive web pages at up 128 kbps compared with thw maximum 56 kbps rate of modem connection. ISDN requires adapters at both ends of the transmission so your access provider also needs an ISDN adapter. ISDN is generally available from your phone company in most urban areas in the United States and Europe. In many areas were DSL and cable modem service are now offered,  ISDN is no longer as popular an option as it was formerly.