N-connected devices phone services that telephone companies using the same cabling that transmits pack- operate. The PSTN comprises traditional etized voice and data. Thus, every device does copper-based telephone lines, central office not need its own power or backup power. switches, fiber-optic cabling, undersea cable systems, cellular systems, microwave con- presence nections, communications satellites, and any The ability of users to know when someone within their community of users is available other system connected via public telephone for realtime or near-realtime messaging. switching centers. It does not include the Internet or carriers' private data networks. PRI (Primary Rate Interface) A form of ISDN with 23 paths for voice, push-to-talk video, and data and one channel for signals. A walkie-talkie type of service pioneered by Each of the 24 channels transmits at 64Kbps. Nextel (now part of Sprint Nextel) in which customers can reach one another by pushing protocol a button on the side of their phone. They also Defines how devices and networks commu- dial an abbreviated telephone number. Push- nicate with one another. For example, a suite to-talk can be used to reach individuals or of protocols known as TCP/IP spells out rules predefined groups. for sending voice, images, and data across the Internet and in corporate networks. QoS (Quality of Service) The ability to offer a number of priorities for proxy server various types of communications including Authenticates callers to ensure that they are voice, e-mail, and video on LANs and WANs. who they say they are before they are sent to their destination. They serve as interme- radio diaries between callers and applications or A wireless device with an antenna that con- endpoints, telephones, and other devices verts signals to and from formats compatible Glossary with the airwaves. Wireless handsets are addresses) and network operators. Encryp- radios. tion is the use of mathematical algorithms to scramble data. RBOC (Regional Bell Operating Company) RSS