ement changed the composition of telephone service in the US when it became effective on, January 1, 1984. document camera A specialized camera that is mounted on a long adjustable neck for taking pictures of still images-pictures, graphics, pages of text and objects-for manipulation such as a video conference. downlink The communications path from a satellite to an earth station. Delivery Multimedia Integration Framework is a session protocol for the management of multimedia streaming over generic delivery technologies. It is similar to FTP except that, where FTP returns data, DMIF returns pointers toward (streamed) data. DOCSIS See Data Over Cable Service Interface Specifications. Glossary of Terms Differential Pulse Code Modulation is a compression technique that sends only the difference between what was (a past frame of video information) and what is (a present frame). DPCM requires identical codecs on each, the transmitting and receiving ends to predict, from a past frame of pixels, what the present frame will be. The transmitting frame, after computing its prediction, compares the actual to its speculation and sends information on the difference. In turn, the receiving codec interprets these differences (called errors) and makes adjustments to the present video frame. driver A driver is software that provides instructions for reformatting or interpreting software commands for transfer to and from peripheral devices and the central processing unit (CPU). Many printed circuit boards require a software driver in order for the other PC components to work correctly. In other words, the driver is a software module that drives the data out of a specific hardware port. Video drivers may be required for desktop video. Digital service, level zero or DS-zero. A single 64 Kbps channel in a multiplexing scheme that is part of the North American and European digital hierarchy and which results from the process of digitizing an analog voice channel through the application of time division multiplexing, pulse code modulat