th, they can be processed and switched at very high speeds. ATM makes it possible to use a single transmission scheme for voice, data, and video traffic on LANs and WANs. cellular A communication service in which voice or data is transmitted by radio frequencies. The service area is divided into cells, each served by a transmitter. The cells are connected to a mobile switching exchange, which is connected to the worldwide telephone network. CELP (Code-Excited Linear Prediction) A vector-quantization-based compression scheme for speech. CELP can compress speech down to 4.8Kbps. There is also a low-end variant called LPC. centrex A local exchange carrier service in which switching occurs at a local exchange rather than at customer-owned PBXs. The telephone company owns and manages all the communica- tions equipment. CEPT (Conférence Européenne des Administrations des Postes et des Télecom- munications [European Conference of Postal and Telecommunications Adminis- trations]) An organization formed by the European PTTs for the discussion of operational and tariff matters. CEPT-0 (or E-0) is the basic increment, and it operates at 64Kbps. CEPT-1 is a 2.048Mbps 32-channel circuit; CEPT-2 is an 8.488Mbps 128-channel circuit; CEPT-3 is a 34.368Mbps 512-channel circuit; CEPT-4 is a 139.246Mbps 2,048-channel circuit; CEPT-5 is a 565.148Mbps 8,192-channel circuit. CERN (Conseil Européen pour la Recherche Nucléaire [European Organization for Nuclear Research]) The world's largest particle physics laboratory and the birthplace of the World Wide Web. channel A logical conversation path. A channel is the frequency band, time slot, or wave- length (also referred to as lambda) over which a given conversation flows. channel bank Equipment typically used in a telephone exchange that performs multiplexing of lower-speed, digital channels into a higher-speed composite channel. The channel bank also detects and transmits signaling information for each channel and transmits framing information SO that time slots allocated to each chann