电子与通信工程硕士专业英语part-6.pptx

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,2020/2/18,#,2025/2/15 周六,1,Lesson 3,电 信,Telecommunications,(UNIT 8 Passage B),Intensive reading,：,1.2.,2025/2/15 周六,2,Lesson 3,电 信,Telecommunications,技术背景,Background,：,The four phases of the evolution of communications networks are shown in Table 8.1,2025/2/15 周六,3,Lesson 3,电 信,Telecommunications,技术背景,Background,：,2025/2/15 周六,4,Lesson 3,电 信,Telecommunications,内容大纲,Outline,：,Hardware and Software,Hardware,Software,Applications,Host-Terminal,File-Transfer,Computer-Network,2025/2/15 周六,5,Lesson 3,电 信,Telecommunications,内容大纲,Outline,：,Telecommunication Services,Network,Information Retrieval,Electronic Mail,Bulletin Board,Ongoing Developments,2025/2/15 周六,6,preface,Lesson 3,电 信,Telecommunications,Telecommunications,are,the,transmission,of,words,sounds,images,or data in the form of electronic or electromagnetic signals or impulses.,Transmission media,include,the telephone(using wire or optical cable),radio,television,microwave,and satellite.,Data communication,the fastest growing field of telecommunication,is the process of transmitting data in digital form by wire or radio.,精读详解,Intensive reading,：,2025/2/15 周六,7,preface,Lesson 3,电 信,Telecommunications,Digital data,can,be generated directly in a 1/0 binary code by a computer,or can,be produced from a voice or visual signal by a process called encoding,.,A data communications network,is created by interconnecting a large number of information sources so that data can flow freely among them.,The data,may consist of,a specific item of information,a group of such items,or computer instructions.,Example,include a news item,a bank transaction,a mailing address,a letter,a book,a mailing list,a bank statement,or a computer program.,精读详解,Intensive reading,：,2025/2/15 周六,8,preface,Lesson 3,电 信,Telecommunications,The devices used,can be computers,terminals,(devices that transmit and receive information),and,peripheral equipment,such as printers.,The transmission line used,can be a normal or a specially purchased telephone line called a,leased,or private line,.It can also,take the form of,a microwave or a communications-satellite linkage,or,some combination of,these various systems.,精读详解,Intensive reading,：,2025/2/15 周六,9,Hardware and Software,Lesson 3,电 信,Telecommunications,Each,telecommunications device,uses,hardware,which connects a device to the transmission line;and,software,which,makes it possible for a device to,transmit information through the line.,Hardware,Hardware usually consists of a,transmitter,and a,cable interface,or if the telephone is used as a transmission line,a,modulator/demodulator,or,modem,.,精读详解,Intensive reading,：,2025/2/15 周六,10,Hardware and Software,Lesson 3,电 信,Telecommunications,A,cable interface,as the name indicates,connects,a device,to,a cable.It,converts,the transmitted signals,from,the form required by the device,to,the form required by the cable.,精读详解,Intensive reading,：,2025/2/15 周六,11,Hardware and Software,Lesson 3,电 信,Telecommunications,Software,Among the different kinds of software are file-transfer,host and network programs.,File-transfer software,is used to transmit a data file from one device to another.,Host software,identifies,a host computer,as such,and controls the flow of data,among devices connected to it.,Network software,allows devices in a computer network to transmit information to one another.,精读详解,Intensive reading,：,2025/2/15 周六,12,Applications,Lesson 3,电 信,Telecommunications,Host-Terminal,In these types of communications,one computer,the host computer,is connected to one or more terminals.,Each terminal,transmits data to or receives data from the host computer.,For example,many airlines have terminals that are located at the desks of ticket agents and connected to a central,host computer.These terminals obtain flight information from the host computer,which may be located hundreds of kilometers away from the agents site.,精读详解,Intensive reading,：,2025/2/15 周六,13,Applications,Lesson 3,电 信,Telecommunications,File-Transfer,An outgrowth of file transfer is,electronic mail,.For example,an employee might write a document such as a letter,memorandum,or report on a computer and then send the document to another employees computer.,精读详解,Intensive reading,：,2025/2/15 周六,14,Applications,Lesson 3,电 信,Telecommunications,Computer-Network,The three kinds of computer networks are,local area networks(LAN),private branch exchange(PBX)networks,and,wide-area networks(WAN).,LANs interconnect devices with a group of cables;the devices communicate at a high speed and must be in close proximity.,精读详解,Intensive reading,：,2025/2/15 周六,15,Applications,Lesson 3,电 信,Telecommunications,A PBX network,interconnects devices with a telephone switching system;in this kind of network,the devices must again be in close proximity.In,wide-area networks,on the other hand,the devices can be at great distances from one another,and such networks usually inter-connect devices by means of telephone.,精读详解,Intensive reading,：,2025/2/15 周六,16,Telecommunication Services,Lesson 3,电 信,Telecommunications,Network,A public network service leases time on a WAN,thereby providing terminals in other cities with access to a host computer.Examples of such services include Telenet,Tymnet,Uninet,and Datapac.These services,sell,the computing power of the host computer,to,users,who cannot or do not wish to invest in the purchase of such equipment,.,精读详解,Intensive reading,：,2025/2/15 周六,17,Telecommunication Services,Lesson 3,电 信,Telecommunications,Information Retrieval,An information-retrieval services leases time on a host computer to customers whose terminals are used to retrieve data from the host.An example of this is CompuServe,whose host computer is accessed by means of the public telephone system.This and other such services provide general-purpose information on news,weather,sports,finances,and shopping.,精读详解,Intensive reading,：,2025/2/15 周六,18,Telecommunication Services,Lesson 3,电 信,Telecommunications,Electronic Mail,Bulletin Board,By means of a,bulletin board,terminals are able to facilitate exchanges and other transactions.Many bulletin boards do not charge a fee for their services.Users of these services simply exchange information on hobbies,buy and sell goods and services,and exchange computer programs.,精读详解,Intensive reading,：,2025/2/15 周六,19,Ongoing Developments,Lesson 3,电 信,Telecommunications,Certain telecommunication methods have become standard in the telecommunications industry as a whole,because if two devices use different standards they are unable to communicate properly.,Standards are developed in two ways:,(1)the method is so widely used that it comes to dominate;(2)the method is published by a standard-setting organization.,精读详解,Intensive reading,：,2025/2/15 周六,20,Ongoing Developments,Lesson 3,电 信,Telecommunications,The most important organization in this respect is the,International Telecommunication Union,a specialized agency of the United Nations and one of its operational entities,the International Telegraph and Telephone Consultative Committee(CCITT).Other organizations in the area of standards are the,American National Standards Institute(ANSI),the,Institute of Electrical Engineers(IEE),and the,Electronic Industries Association,.,精读详解,Intensive reading,：,2025/2/15 周六,21,Ongoing Developments,Lesson 3,电 信,Telecommunications,One of the goals of these organization is the full realization of the,integrated services digital network(ISDN),which is projected to be capable or transmitting through a variety of media and at very high speeds both voice and non-voice data around the world in digital form.,精读详解,Intensive reading,：,2025/2/15 周六,22,Ongoing Developments,Lesson 3,电 信,Telecommunications,Other developments,in the industry are aimed at increasing the speed at which data can be transmitted.Improvements are being made continually in modems and in the communications networks.Some public data networks support transmission of 56,000 bits per second(bps),and modems for home use are capable of as much as 28,800 bps.,精读详解,Intensive reading,：,2025/2/15 周六,23,