ISDN (Integrated Services Digital Network) provides digital communication channels for voice, data and other network services over ordinary telephone copper wires. It supports basic rate interface (BRI) lines with two 64 kbps digital channels for voice and data, and primary rate interface (PRI) lines for larger installations with 23 digital channels. A terminal adapter (TA) is used to connect non-ISDN devices to the ISDN network, converting signals between digital ISDN and analog formats. ISDN allows remote access to local area networks and all telephone calls are converted to digital form for transmission.

2. BRI (Basic Rate Interface) This lines provide two data channels. > bearer channels. > B channels. Each independent B channels carries Voice or Data at 64 kbps. PRI (Primary Rate Interface) This lines provide 23 B-channel for large installations.