Isdn contined

There are two classifications of isdn.. Narrow band ISDN and Broadband ISDN.For broadband ISDN packet switching should be used.In our country that is not implemented.In narrow band Isdn itself there are two groups - PRI and BRI.usually PRI connections are taken by customers who require more bandwidth.so let us analize the term isdn...IS--means Integrated services....For a single telephone connection extending from the exchange to customer premises,the subscriber can enjoy only one service at a time...(either voice,or data or fax like that).But In isdn these services can be integrated..ie voice,fax,data ...can be made available simultaneously.Then DN---Digital Network means...right from the exchange to customer end in the digital format.since it is in the digital format...some coding techniques should be employed.