电信专业英英词典D-3（在线收听）

　　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.