DAMA - Stands for Demand-Assigned Multiple Access. This is a way to instantaneously assign telephony channels in a transponder according to the immediate traffic demands.

　　Dash - This is the the character "-".

　　Data - This term typically refers to anything that is not a voice, and it is, according to AT&T, "a representation of facts, concepts or instructions in a formalized manner, suitable for communication, interpretation or processing."

　　Database - This term refers to a collection of data that is catalogued in a logical way to ensure quick and reliableaccess.

　　Data Carrier Detect (DCD) - This is a hardware signal that indicates when a modem is online and capable of transmission.

　　Data Communications Equipment (DCE) - This is a device that translates a digital signal from data terminal equipment (DTE) into a form acceptable to the receiving device.

　　Data Compression - This is when data file size is reduced by elimination unnecessary information.

　　Data Grade Circuit - This is a circuit, such as a phone line, that is capable and suitable for transmitting data.

　　Data Link - This term describes communications paths that are used for data transmissions.

　　Data Set - (1) According to AT&T a data set is modem, but (2) according to IBM, a data set is a collection of data.

　　Data Set Ready (DSR) - This is a control signal that says that says a modem is ready to begin initial stages of transmission (i.e., configuration).

　　Data Terminal Equipment (DTE) - This is equipment that only receives information (i.e., no transmission), such as a printer.

　　Data Terminal Ready (DTR) - This is another control signal that says that modems have completed their initial configuration session and are ready for transmission.

　　DBS - This stands for Direct Broadcast Satellite, and refers to service that uses satellites to broadcast multiple channels of television programming to home mounted small-dish antennas, such as those provided by DirecTV or Dish Network.

　　dBi - The dB power relative to an isotropic source.

　　dBW - The ratio of the power to one Watt; it is expressed in decibels.

　　DCD - see Data Carrier Detect.

　　DCE - see Data Communications Equipment.

　　Decibel (dB) - The standard unit used to express the ratio of two power levels. In the communications field, It is used to express either a gain or loss in power after the signal has traveled between the input and output devices.

　　Declination - The offset angle of an antenna from the axis of its polar mount.

　　Decoder - Also called a receiver, this is a television-top device that converts an electronically scrambled television picture into a signal viewable on the TV.

　　Deemphasis - Reinstatement of a uniform baseband frequencyresponse following demodulation.

　　Default - This is the factory setting or configuration of software or hardware.

　　Delay - This is the wait time between to specific events, and regardingsatellite communications, it is the time it takes for a signal to go from the transmission station up to orbit and through the satellite and back down to the receiving earth station (about 1/4 of a second).

　　Delete - This terms means to discard (i.e., destroy) information.

　　Delivery on-orbit - A contractual term describing a service to deliver the satellite at its intended orbital location in space.

　　Demodulation - This is the process of extracting the electrical signal (i.e., the data) from the carrier signal.

　　Demodulator - A satellitereceiver circuit which extracts or "demodulates" the desired data from from the received carrier signal.

　　Deviation - The modulation level of an FM signal determined by the amount of frequency the signal is from the frequency of the main carrier signal.

　　Dial - This refers to the sending out of either pulses or tones with the intent of establishing a connection (i.e., a circuit) with another phone or modem.

　　Dialup Modem - This is a modem that is used over normal telephone lines (i.e., not DSL or cable)

　　Dial String - This is the string of characters used to contact another device over telephone lines.

　　Dial Tone - This sound signifies that a telephone is ready to receive instruction (i.e., make a call).

　　Dibit - This is group of two bits.

　　Digital - Referring to communications techniques whereby information and data are encoded as discrete elements in a binary language, as opposed to analog representation of information in variable, but continuous, wave forms.

　　DIP - This is the act of extracting particular information from a database.

　　Diplexer - This is a device which combines two transmitters onto one single transmission line.

　　Dipole - This is an antenna that is fed from the center (such as rabbit ears).

　　Disconnect - To break a connection (i.e., a circuit) so communication is no longer possible.

　　Domain - On the internet, a domain is a place to visit with your internet browser.

　　Door - This is a software program that allows BBS users to run a program while a user is simultaneously using the BBS.

　　Down - This is a general term that means that something is not currently working.

　　Downlink - The segment of a satellite circuit that extends from the satellite to the user terminal (such as, but not limited to, a television).

　　Download - This term means to receive data from another source.

　　Driver - This is a software program that provides instructions to a computer on how to communicate with peripheral devices, such as printers or modems.

　　DTE - see Data Terminal Equipment.

　　DTMF - see Dual Tone Multi-Frequency.

　　DTR - see Data Terminal Ready.

　　DTV - Stands for Digital Television.

　　Duplex Transmission - This is the capability for simultaneous data transmission between a sending and receiving station.

　　Dual Tone Multi-Frequency (DTMF) - This is when two tones are used to represent each digit dialed on a telephone.

　　Dumb Switch - This is a switch that contains only basic switching equipment and need to be instructed by an outside source.

　　Dumb Terminal - This is a terminal with no programming or processing capabilities, and it is used primarily for information entering.

　　Duplex - (1) This term refers to the condition where two-way, simultaneous transmission is possible. (2) It is also the technical term for a common, electrical wall outlet.

　　DVB - This stands for Digital Video Broadcasting and is the European-backed project to standardize elements of digital video.

　　补充：

　　Dedicated Service - A connection to the Internet using a leased line that provides for very fast, high bandwidth connections. Also called permanent direct service.

　　Digital - An advanced type of radio transmission that broadcasts voice or data intact via radio waves, which allows for greater call clarity, advanced wireless features and improved voice capacity. The industry uses three types of digital technology: TDMA, CDMA and GSM.

　　Dialup Service - A connection that allows you to access the Internet by dialing into a computer through a modem and telephone line.

　　Directory - While there is no single source or official Internet directory, there are several search vehicles available to research or access information on the WWW. Directories categorize and list information in specific headings or categories.

　　DNS - See Domain Name System

　　Domain Name - A unique name that identifies an Internet site; the Domain Name will always have at least two parts separated by dots (for example: tds.net or tdsnet.com). These names are granted and controlled by a centralized Internet Network Information Center (InterNIC), administered by the National Science Foundation.

　　Domain Name System (DNS) - A system by which one Internet host can find another. DNS translates words (Domain Names) into numbers that Internet computers can understand.

　　Download - To transfer of a file or information from another computer to yours.

　　Digital Subscriber Line (DSL) - A DSL line transmits simultaneous voice and high-speed data over existing copper telephone wires without the need of additional phone lines.

　　D type Channel Bank

　　A D type channel bank is channel termination equipment used for combining (multiplexing) individual analog channel signals on a time division basis. D type channel banks provide interfaces for "n" analog signal inputs. Each analog input signal is directed to a codec for en coding to PCM samples. A part of a Tl carrier system.

　　DACS

　　digital access & cross-connect system

　　DARPA

　　Defense Advanced Research Projects Agency

　　Data Compression

　　Data compression is a technique that removes redundancy in transmitted bit patterns to reduce transmission rates by 20% to 200%. For example, a modem designed to send and receive data at 1200 bps without data compression may be capable of supporting 2400 bps with data compression, using the same network analog voice-grade channel.

　　Data Service Units (DSU)

　　DSUs are channel service units (CSI's) and data service units (DSUs) are required to connect digital customer premises equipment (CPE ) to carriernetworks. A hardware device providing an interface between a digital line and a unit of data terminal equipment. DSUs provide transmit and receive control logic, synchronization and timing recovery across data circuits. DSUs may also convert ordinary binary signals generated by CPE to special bipolar signals. Bipolar signals are designed specifically to facilitatetransmission at up to 1.544 Mbps rates over UTP cable, a media originally intended for 3 kHz, voice bandwidth signals. See Channel Service Units (CSU).

　　Data Terminal Equipment (DTE)

　　DTE is any device that can send data, receive data or perform both functions. (Note: sometimes DTE implies digital terminal equipment, a type of CPE used with digital Service--see CSU and DSU.)

　　DB Loss

　　Decibel (dB) is a unit of measure of signal strength, usually the relationship between a transmitted signal and a standard signal source. Loss is measured when the signal received across a communication circuit is less than what was transmitted by the signal generator.

　　DCE

　　data circuit terminating equipment

　　DCP

　　digital communications protocol

　　DCS

　　digital cross-connect system

　　DDD

　　direct distance dialing

　　DDN

　　Defense Data Network

　　Digit L

　　Digital L is another amplitude condition that represents a binary digit 0. See binary digit or bit.

　　Digital Carrier Systems

　　Digital Carrier Systems are carrier systems for digital signals that uses regenerative versus linear repeaters and time division multiplexing.

　　Digital Cross Connect System (DCS)

　　DCS is a new generation of switching/multiplex equipment that permits per-channel DS0 (64 kbps) electronic cross-connection from one T1 transmission facility to another, directly from the constituent DSl signals. Commonly referred to as "DACS" (digital access and cross connect system), although this is a trademark of AT&T.

　　Digital Signal

　　A digital signal is a signal (electrical or otherwise) in which information is carried in a limited number of different (two or more) discrete states. The most fundamental and widely used form of the digital signal is binary, in which one amplitude condition represents a binary.

　　Digital Termination Service (DTS)

　　DTS is a service provided by some carriers permitting opera tors of private networks to use digital microwave equipment to gain access to carrier net works. The FCC has allocated a special microwave band for DTS.

　　Direct Inward Dialing (DID)

　　DID is PBX-to-central office trunks that allow incoming calls to a PBX to ring specific stations without attendant assistance. DID greatly reduces the number of required console attendants, compared with systems in which all calls must be extended by console attendants.

　　Direct Outward Dialing (DOD)

　　DOD is PBX-to-central office trunks that allow outgoing calls to be placed directly by PBX stations.

　　Dispersion

　　In dispersive media, dispersion are complex signals are distorted because the various frequency components which make up the signal have different propagation characteristics and paths. Due to the finite conductivity of copper, wire or cable media for guided wave transmission is fundamentally dispersive. Dispersion limits the upper bit rate that a medium can support by distorting the signal waveforms to the extent that transitions from one information state to another cannot be reliably detected by receiving equipment, (e.g., logical l logical 0 value changes).

　　DLCI

　　data link connection identifier

　　DOD

　　direct outward dialing

　　DQDS

　　distributed queue dual bus

　　DS"N" Digital Signal Hierarchy

　　A time division multiplexed hierarchy of standard digital signals used in telecommunications systems. DS1 level in the hierarchy corresponds to a 1.544 Mbps TDM signal which comprises 24 DS0 signals. DS0 refers to individual digital signals at channel rates of 64 kbps. Four DS1 signals digitally multiplexed produce a DS2 level signal, containing 96 DS0 channels, and requires a transmission medium that supports 6.312 Mbps. A DS3 level signal results from the digital multiplexing of 7 DS2 signals, supports 672 DS0 signals and requires a 44.736 Mbps transmission medium. Finally a DS4 level signal supports 6 DS3 level signals, 4032 DS0 signals and requires a 274.176 Mbps transmission medium. The DS hierarchy accounts for non synchronism in the multiplexing plan, hence the term "asynchronous digital hierarchy" and the use of overhead bits. Note that bit rates at higher levels are not integer multiples of 64 kbps.

　　DSP

　　digital signal processor

　　DSS/BLF

　　direct station selection/busy lamp field

　　DSS

　　digital subscriber service

　　DSU

　　data service unit

　　DTMF

　　dual tone multiple frequency

　　DTS

　　digital termination service

　　Dual-Tone Multiple Frequency (DTMF)

　　the generic name for the tone signaling scheme used to signal from telephones to switching equipment, in which 10 decimal digits and two auxiliary characters are represented by selecting two frequencies of the following group: 697, 770, 852, 941,1209,1336,1447 Hz.
关键字:电信专业英英词典
生词表: