D

	DBS (Direct broadcast videoconference)
	Refers to a service that uses videoconferences to broadcast multiple channels of television programming directly to home mount small-dish antennas.
	D Channel
	A channel that carries WAN synchronization information on a line using ISDN D-channel signalling.
	Delay
	The time it takes for a signal to go from the sending station through the videoconference to the receiving station. This transmission delay for a single hop videoconference connection is very close to one-quarter of a second.
	Demodulator
	A videoconference receiver circuit that extracts or "demodulates" the "wanted" signals from the received carrier.
	Desktop videoconferencing
	Videoconferencing on a personal computer. Most appropriate for small groups or individuals. Many desktop videoconferencing systems support document sharing. (See Room-based videoconferencing).
	Digital Signal
	A way of sending voice, video, or data that reconstructs the signals using binary codes (1s and 0s) for transmission through wire, fibre optic cable, videoconference, or over air techniques. Digital audio/video signals represented by discrete variations (in voltage, frequency, amplitude, location, etc.) can be transmitted faster and more accurately than analogue signals.
	Distance learning
	The incorporation of video and audio technologies so that students can "attend" classes and training sessions that are being presented at a remote location. Distance learning systems are usually interactive and are becoming a highly valuable tool in the delivery of training and education to widely dispersed students or in instances where the instructor cannot travel to the student's site.
	Document sharing
	A feature supported by many videoconferencing systems that allows participants of a videoconference to view and edit the same computer document.
	Domain Name
	In the Internet, a part of a naming hierarchy consisting of a sequence of names separated by periods (dots) that corresponds to the network number in the IP address. In the symbolic name phil@vitalphase.co.uk, the domain name is vitalphase.co.uk.
	DTE (Data Terminal Equipment)
	As defined in the RS-232 specification, equipment to which DCE (Data Communications Equipment) is connected, such as a videoconference terminal, LAN bridge or router.
	Dual 56
	Two switched 56 calls made between videoconferencing equipment to allow data transfer at 112 kbps. The videoconferencing equipment performs a two-channel inverse-multiplexing procedure to assure channel alignment.
	DVB (Digital Video Broadcast)
	The standard for direct broadcast television in Europe and the U.S. Based on MPEG2 Compression.