ion and North American or European companding. (T-1). A multiplexing scheme that is part of the North American digital hierarchy and which specifies how to subdivide 1.544 Mbps of bandwidth into twenty-four 64 Kbps channels using time division multiplexing, pulse code modulation and North American companding. Europe has a similar multiplexing hierarchy that produces a 2.048 Mbps signal (E- 1/CEPT). Also called T-3. A multiplexing scheme that is part of the North American digital hierarchy and which specifies how to subdivide 45 Mbps of bandwidth into 28 T-1 (1.544 Mbps) carrier systems-a total of Video Communication: the Whole Picture 672 channels. The techniques for accomplishing this include time division multiplexing, pulse code modulation and North American companding. Digital signal processor. A specialized computer chip designed to perform speedy and complex operations on digitized waveforms. Useful in processing sound and video signals. Data service unit. A device used to transmit digital data on digital transmission facilities. It typically interfaces to data terminal equipment via an RS-232- C or other terminal interface, connecting this device to a DSX-1 (digital system cross connect) interface. Digital Signal Cross-Connect, a panel that connects digital circuits to allow cross-connections via a patch and cord system. Data terminal equipment. The equipment side of an equipment to network connection with DCE, data communications equipment connecting the DTE to the network for the purposes of transmission. dual 56 Combination of two 56 Kbps lines (usually switched 56) to yield a 112 Kbps channel used for low- bandwidth videoconferencing. Dual 56 allows for direct dialing of a videoconference call and can be obtained from IXCs or LECs. Digital Video Cassette. A DVC is a storage medium based on a _-inch-wide tape made up of metal particles. The DVC source is sampled at a rate similar to that of CCIR-601 but additional chrominance subsampling (4:1:1 in the NTSC 30 kHz mode) provides better resolutions. When 