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Integrated Services Digital Network (ISDN) is a circuit switched telephone network system, designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher speeds, than available with analog systems. More broadly, ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the end user.
The most common viewpoint is that of the end user who wants to get a digital connection into the telephone/data network from home, whose performance would be better than an ordinary analog modem connection. The typical end-user's connection to the Internet is related to this point of view, and talk about the merits of various ISDN modems, carriers' offerings is from this perspective. As a data connection service, ISDN has been mostly superseded by DSL. There is however a second viewpoint: that of the telephone industry, where ISDN is growth potential. A telephone network can be thought of as a collection of wires strung between switching systems.
