Three lines into voice over IP

n Gateway. A gateway sits between a telephone system, such as a private

branch exchange (PBX) or a central office switch, and a data network, such

as the Internet, and translates calls from one format to another.

n Internet Protocol PBX. An IP, or software, PBX is a specialized computer

system that replaces a company's traditional voice system. The devices support

IP voice transmissions all the way down to a user's desktop.

n Integrated voice and data system. Such systems treat voice over IP

as just another application on a corporate LAN. These systems often have

a number of functions, such as messaging, in a device geared to handle a

company's data and voice needs.