高级通信工程师考试复习题.pdf

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1、通信英语强化训练试题（一）通信英语强化训练试题（一）单项选择题:(Choose the best one)()1.()2.()3.()4.()5.()6.()7.()8.()9.()10.Furthermore,we shall prove that a minimum theoretical sampling frequency of order 6.8 kHz is required _a voice channel _the range 300Hz to 3.4 kHz。A。convey,occupyB.to convey,occupyingC.conveying，occupiedD.c

2、onvey,to occupyFor example,the signal _from a satellite,_in far outer space,isvery weak.A.received,locatedB。receive，locateC.receiving,locatingD.to receive,to locateIf we consider binary transmission,the complete information about a particular messagewill always _by simply _the presence or absence of

3、 the pulse.A。obtain,detectB.be obtained，detectingC。obtained，detectedD.obtaining,detected4.There is an inherent advantage for _noisy environments by_digital transmission.A。overcoming,chooseB.overcome,choosingC。overcome,chooseD.overcoming，choosingEach voice channel has a separate coder，the unit _conve

4、rts sampledamplitude values to a set of pulses；And decoder,the unit _performs thereverse operation.A。who,whoB.when，whenC。where，whereD.that,thatThe problem is easily overcome by _a frame format,where at the start ofeach frame a unique sequence of pulses is placed _the start of the frame.A。specify，ide

5、ntifyB.specifying，so as to identifyC。specified,identifiedD.specify，identifyingAn asynchronous serial data link is said _character oriented，asinformation is transmitted in the form of groups of bits _characters.A.be，callingB。to being，to callC。been，callD.to be，calledThis interface is so called because

6、 the _data and the _data arenot synchronized over any extended period.A.transmit，receiveB.to transmit，to receiveC.transmitting，receivingD。transmitted，receivedSerial data transmission systems _in the telephone，Morse code,andeven the smoke signals once _by native Americans。A。are finding，usingB。are fou

7、nd，usedC。find,useD。be found，usingTraditionally，the idle state _the mark level.By convention thiscorresponds _a logical 1 level.A。is referred to，asB。is referred as,inC,is referred to as,toD.is referred，within1()11.The transmitter then sends the character，1 bit at a time，by _eachsuccessive bit on the

8、line for a duration of T seconds,_all bits have beentransmitted。A.place,stillB。placed,sinceC。placing,untilD。placing，because()12.WhenthedatalinkconnectsaCRTterminal_acomputer,_problems arise,as the terminal is itselfcharacter oriented。A.into,manyB.on，a fewC.in，a fewD。to，few()13._the receiving end of

9、a synchronous serial data link，the receivercontinually monitors the line _a start bit.A.On，lookingB.Within，look forC.In，look atD。At,looking for()14.As companies realized they could save money and gain productivity by_networkingtechnology,theyaddednetworksandexpanded_networks almost as rapidly as new

10、 network technologies and productscould be introduced。A.use,existB。using，existingC.to use，to existD。used，existed()15.The OSI reference model allows you _the network functions that occurat each layer。More importantly,the OSI reference model is a framework you canuse _how information travels throughou

11、t a network。A。view,understandB。viewing,understandingC。viewed,understoodD.to view,to understand()16.The transport layer segments data from the _hosts system andreassembles the data into a data stream on the _hosts system。A。sending，receivingB.to send,to receiveC.sent,receivedD。send,receive()17.The dat

12、a link layer provides the transit of data _a physical link。In sodoing，the data link layer is concerned _physical addressing，networktopology，network media access,and error detection。A.with,acrossB.at,inC.between,inD。across，with 短语英译汉：(Translate the following phrases into Chinese）1.the schemes for per

13、forming these three functions2.a series of amplitude values3.a speech channel of telephone quality24.a sequence of 8binary digits5.a minimum theoretical sampling frequency6.a voice channel occupying the range 300 Hz to 3。4 kHz7.8digits per sample value8.the sparking of a car ignition system9.the str

14、eam of the pulses with a repetition rate of 64 kHz10.the relationship of the true signal to the noise signal11.the signal received from a satellite12.the complete information about a particular message13.the shape of the transmitted signal14.the attenuation introduced by transmission path15.the unit

15、 that converts sampled amplitude value to a set of pulses16.a sequence relating to channel 1，2 and so on17.a unique sequence of pulses called synchronization word18.terrestrial system319.the presence or absence of the pulse20.a highspeed electronic switch21.the time division multiplexer22.Time Divis

16、ion Multiplexing23.asynchronous serial data transmission24.the most popular serial interface25.the transmitted data26.the clocks at the transmitter and receiver27.the era of teleprinter28.the dots and dashes of a character29.three times the duration of intersymbol space30.the group of bits called ch

17、aracters31.the invariable units comprising 7 or 8 bits of information32.a clock generated locally by the receiver33.the received parity bit following the character434.the falling edge of the start bit35.the characteroriented nature of the data working technology37.proprietary networking system38.the

18、 International Organization for Spatibility between the various types of networks40.seven numbered layers41.standardization of network components42.error recovery43.receiving hosts system44.connectionoriented circuits45.information flow work work media access48.electrical specification549.maximum tr

19、ansmission distance 短语汉译英：（Translate the following phrases into English）1.2.3.抽样量化与编码27.发送器与接收器话路28.数据传输幅值29.数据流4.抽样频率5.抽样速率6.脉冲流7.重复率8.编码过程9.模拟信号10.传输质量11.数字通信12.数字传输13.含噪声的环境14.传输路由15.信噪比16.信号电平17.地面系统18.噪声功率19.二进制传输20.反向操作21.8 位码序列22.接收端23.帧格式24.同步字25.串行接口26.显示终端30.31.32.33.34.35.36.37.38.39.40.4

20、1.42.43.44.45.46.47.48.49.50.51.52.6闲置状态传号电平空号电平起始位停止位T 秒的持续时间奇偶校验位错误标志传输错误下降沿符号间的空格接收机的定时本地时钟磁带控制比特逻辑 1 电平二进制数据明显的缺点联网技术国际标准化组织参考模型数据分组应用程序53.网络媒体54.分层59.网络服务60.文件接入55.硬件和软件61.数据格式56.表示层57.传输层62.主机63.协议58.数据链路层64.连接65.逻辑选址 请将下述短文译成中文(短文英译汉）：（Translate the following passages into Chinese)1.1.If we c

21、onsider binary transmission，the complete information about a particular messagewill always be obtained by simply detecting the presence or absence of the pulse.Bycomparison，most other forms of transmission system convey the message information usingthe shape,or level of the transmitted signal；parame

22、ters that are most easily affected by thenoise and attenuation introduced by the transmission path。Consequently there is an inherentadvantage for overcoming noisy environments by choosing digital transmission。2.2.The reader may ask,how does the demultiplexer know which group of 8 digits relatesto ch

23、annel 1，2，and so on?Clearly this is important!The problem is easily overcome byspecifying a frame format，where at the start of each frame a unique sequence of pulses calledthe frame code，or synchronization word,is placed so as to identify the start of the frame.Acircuit of the demultiplexer is arran

24、ged to detect the synchronization word，and thereby itknows that the next group of 8digits corresponds to channel 1.3.3.Noise can be introduced into transmission path in many different ways;perhaps via a nearbylightning strike,the sparking of a car ignition system，or the thermal lowlevel noise within

25、 thecommunication equipment itself。It is the relationship of the true signal to the noise signal,knownas the signal tonoise ratio,which is of most interest to the communication engineer.74.4.Basically,if the signal is very large compared to the noise level，then a perfect messagecan take place；howeve

26、r,this is not always the case。For example,the signal received from asatellite，located in far outer space，is very weak and is at a level only slightly above that ofthe noise.Alternative examples may be.Found within terrestrial systems where,although themessage signal is strong，so is the noise power。5

27、.5.So far we have assumed that each voice channel has a separate coder,the unit thatconverts sampled amplitude values to a set of pulses;and decoder,the unit that performsthereverse operation.This need not be so，and systems are in operation where a single codes isshared between 24，30，or even 120 sep

28、arate channels。6.6.A high-speed electronic switch is used to present the analog information signal of eachchannel，taken in turn，to the codec。The codec is then arranged to sequentially sample theamplitude value,and code this value into the 8digit sequence。Thus the output to the codecmay be seen as a

29、sequence of 8 pulses relating to channel 1，then channel 2，and so on。Thisunit is called a time division multiplexer。7.7.An asynchronous serial data link is said to be characteroriented，as information istransmitted in the form of groups called characters.These characters are invariable unitscomprising

30、 7 or 8 bits of information plus 2 to 4 control bits and frequently correspond toASCII-encoded characters。Initially，when no information is being transmitted,the line is inan idle state。The idle state is referred to as the mark level and corresponds to a logical 1 level.88.8.When the transmitter wish

31、es to send data,it first places the line in a space level for oneelement period。The transmitter then sends the character,1 bit at a time,by placing eachsuccessive bit on the line for a duration of T seconds,until all bits have been transmitted.Then asingle parity bit is calculated by the transmitter

32、 and sent after the data bits.Finally,thetransmitter sends a stop bit at a mark level for one or two bit period。9.9.At the receiving end of an asynchronous serial data link，the receiver continually monitorsthe line looking for a start bit。Once the start bit has been detected,the receiver waits until

33、 the end ofthe start bit and then samples the next N bits at their centers,using a clock generated locally by thereceiver.As each incoming bit is sampled，it is used to construct a new character。10.10.The most obvious disadvantage of asynchronous data transmission is the need for a start,parity,and s

34、top bit for each transmitted character.If 7 bit characters are used，the overallefficiency is only 70 percent。A less obvious disadvantage is due to the character-orientednature of the data link。Whenever the data link connects a CRT terminal to a computer，fewproblems arise，as the terminal is itself ch

35、aracter oriented。11.11.The most critical aspect of the system is the receiver timing。The falling edge of the startbit triggers the receivers local clock,which samples each incoming bit at its nominal center.Suppose the receiver clock waits T/2 seconds from the falling edge of a start bit and samples

36、 theincoming data every T seconds thereafter until the stop bit has been sampled.As the receiversclock is not synchronized with the transmitter clock，the sampling is not exact。912.12.By far the most popular serial interface between a computer and its CRT terminal is theasynchronousserial interface。T

37、his interface is so called because the transmitteddata and thereceived data are not synchronizedover any extended period and therefore no special means ofsynchronizing the clocks at the transmitter and receiver is necessary。In fact，the asynchronousserial data link is a very old form of data transmis

38、sion system and has its origin in the era of theteleprinter.13.13.Most computer terminals transmit and receive ASCII characters，and we know that theASCII characters require 7 bits。Therefore,7 bits of data plus a parity bit are sent each time acharacter is transmitted or received by the terminal.The

39、two most obvious ways to send thecharacters are by parallel transmission or by serial transmission.Most terminals have beendesigned to transmit and receive ASCII characters as serial data.14.14.The early development of LANs，MANs,and WANs was chaotic in many ways.Theearly 1980s saw tremendous increas

40、es in the numbers and sizes of networks.As companiesrealized they could save money and gain productivity by using networking technology，theyadded networks and expanded existing networks almost as rapidly as new network technologiesand products could be introduced。15.15.Proprietary systems are privat

41、ely developed,owned，and controlled.In the computerindustry，proprietary is the opposite of open.Proprietary means that one or a small group ofcompanies controls all usage and evolution of the technology。Open means that free usage ofthe technology is available to the public.1016.16.The OSI reference m

42、odel allows you to view the network functions that occur at eachlayer。More importantly，the OSI reference model is a framework you can use to understandhow information travels throughout a network。In addition,the OSI reference model can beused to visualize how information,or data packets，travels from

43、 application programs,througha network medium，to other application programs that are located in another computer on anetwork,even if the sender and the receiver have different types of network media.17.17.The application layer is the OSI layer that is closest to the user.It provides networkservices，

44、such as file access and printing，to the users applications。It differs from the otherlayers in that it does not provide services to any other OSI layer,but rather，only toapplications outside the OSI model.The application layer establishes the availability of intendedcommunication partners。It also syn

45、chronizes and establishes an agreement on procedures forerror recovery and control of data integrity.18.18.The transport layer attempts to provide a data transport service that shields the upperlayers from transport implementation details.Specifically，such issue as how reliable transportbetween two

46、hosts is accomplished in the concern of the transport layer.In providingcommunication service，the transport layer establishes，maintains，and properly terminatesconnection-oriented circuits.In providing reliable service,transport errordetection-andrecovery and information flow control are used.19.19.T

47、he physical layer defines the electrical,mechanical,procedural,and functionalspecifications for activating,maintaining,and deactivating the physical link between endsystems.Such characteristics as voltage levels,timing of voltage changes，physical data rates,maximum transmission distances,physical co

48、nnectors,and other,similar,attributes are defined11by physical layer specifications.阅读理解：(Trueor false statement）Accordingtothefollowing textsdecidewhetherthestatements following the texts are true(T）or false(F)PASSAGE ONEDigital transmission provides a powerful method for overcoming noisy environme

49、nts。Noisecan be introduced into transmission path in many different ways：perhaps via a nearby lightningstrike,the sparkingof a car ignition system,or the thermallowlevelnoise withinthecommunication equipment itself.It is the relationship of the true signal to the noise signal,knownas the signal-to-n

50、oise ratio，which is of the most interest to the communication engineer.Basically,ifthesignal isverylargecompared tothenoiselevel,thena perfect message can takeplace；however，this is not always the case。For example,the signal received from a satellite，locatedin far outer space，is very weak and is at a