D-AMPS (Digital Advanced Mobile Phone System). The U.S. technical standard for digital mobile phone system.

Data Carousel. A DVB data broadcasting service that allows a server to present data modules to a decoder, by cyclically repeating the contents of the carousel, for example Teletext.

Data compression. The general term for the various algorithms and programs developed to transmit data in a format that saves storage space. A compression program is used to convert data from the original format to one optimized for compactness. A decompression algorithm returns the information to its original format.

Datagram. Another term used to describe an information packet.

Datalink layer. The second layer of the OSI model for data communications. The datalink layer contains protocols for the construction of frames, frame addressing, and the detection of errors on a link.

Data Piping. A DVB data broadcasting service that supports a simple, asynchronous delivery. It is carried directly in the payloads of MPEG-2 / TS packets.

Data rate. The amount of information that can be sent down a channel in a given time. In analog systems, data rate is measured in terms of bandwidth. In digital systems, it is measured in bits per second.

Data Streaming. A DVB data broadcasting service that supports a streaming-oriented, end-to-end delivery, in either of three ways: asynchronous, synchronous or synchronized (with other streams).

dB (decibel). A logarithmic measure of relative signal strength which is a convenient means of describing signal powers that vary over a very wide range of values.

DBS (Direct Broadcast Satellite). Direct satellite TV broadcast by program providers, using the frequency band of 11.70 to 12.40 GHz.

DCT (Discrete Cosine Transform). A DVB / MPEG-2 algorithm that facilitates intra-frame coding, by concentrating the signal energy in only a few coefficients.

DDS Direct Digital System. A network whose infrastructure equipment is completely digital. All signals on such a network are transmitted digitally and there is no need for analog-to-digital converters.

Deck. A collection of WML cards.

DECT (Digital Enhanced Cordless Telecommunications). A digital standard for wireless telecommunications. Unlike GSM, which is suited when roaming over large geographical areas, DECT is designed for a smaller area such as a city. DECT is becoming increasingly popular as an alternative for homes and business, to the ordinary fixed network telephone service. DECT uses TDMA to transmit radio signals within the network. A user can have a telephone (known as dual-mode phone) that can seamlessly operate with both GSM and DECT.

Device. A network entity that is able to transmit and receive information packets.

DHCP (Dynamic Host Configuration Protocol). An IETFstandard that automatically configures hosts, using a DHCP server.

DID (Direct Inward Dialing). Making a call directly to a desired extension number without needing to speak with the switchboard operator.

Digital. A method of transmitting voice signals or data. Digital signals are represented in binary format.

Digital Compression. A process of translating analog signals into a digital code that has a reduced bit rate than the original signal would have. It does this by removing redundant and irrelevant information.

Data line interface. The connection point for a telephone.

Downlink. The transmission of radio frequency (RF) signals down a hierarchy of infrastructure equipment. For example, from a satellite to a ground communications station, from a mobile services switching center (MSC) to a base station controller (BSC); from a BSC to a base transceiver station (BTS).

DSP (Digital Signal Processing). DSP is a modern digital technique for processing signals. It allows complex operations to be performed very cost effectively through the use of microprocessor-based integrated circuits.

DS-CDMA: Direct Sequence CDMA. DS-CDMA is a form of spread spectrum modulation.

DS-SS (Direct Sequence-Spread Spectrum). DS-SS is a form of spread spectrum modulation in which the narrowband information-bearing signal is spread over a wide range of frequencies through direct multiplication with a pseudo-random binary sequence.

DT (data Terminal). Any equipment that acts as a source of data signals or a receiver of data signals.

Dual-mode phone. A phone that can operate on both analog and digital networks.

Duplex. Simultaneous, bidirectional independent transmission of data.

DVB (Digital Video Broadcasting). Originally a European standard for digital radio and TV broadcasting, it has now been adapted worldwide. It uses MPEG-2 digital compression.