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. There are two levels of service: Basic Rate Interface (BRI), intended for the home and small enterprise, and Primary Rate Interface (PRI), for larger users. Both rates include a number of B channels and a D channel. Each B channel carries data, voice, and other services, whereas the D channel carries control and signaling information. In general, ISDN is the integration of both analog or voice data together with digital data over the same network. ISDN uses signaling protocols to set up, control and terminate calls. This signaling protocol is formally specified in ITU-T Q.921 and Q.931. Group all ISDN FAS interfaces sharing the same ISDN parameters. Each interface contained in this group shall have defined a D-Channel.