复习资料一《专业英语》词和词组缩略写

1、复习资料一：专业英语词和词组 缩略写Unit 11 抽样 量化 编码 sampling quantizing coding2 话路 speech channel3 幅值 amplitude value4 抽样频率 sampling frequency5 抽样速率 sampling rate6 脉冲流 stream of pulses7 重复率 repetition rate8 编码过程 coding process9 模拟信号 analog signal10 传输质量 transmission quality11 数字通信 digital communication12 数字传输 digita

2、l transmission13 噪声环境 noisy environment14传输路径 transmission path15 信噪比 signal to noise ratio16 信号电平 signal levels17 地面系统 terrestrial system18 噪声功率 noise power19 二进制传输 binary transmission20 反向操作 reverse operation21 8位码序列 8-digit sequence22 接收端 receiving terminal23 帧格式 frame format24 同步字 synchronizatio

3、n word25 时分复用 TDM Unit 21 串行接口 serial interface2 显示终端 CRT terminal3 发送器和接受器 transmitter and receiver4 数据传输 data transmission5 数据流 data stream6 空闲状态 the idle state7 传号电平 mark level8 空号电平 space level9 起始位 start bit10 停止位 stop bit11 持续时间T秒 duration of T seconds12 奇遇校验位 parity bit13 错误标志 error flag14 传输

4、错误 transmission error15 下降沿 falling edge16 符号间的空格 intersymbol space17 接收机的定时 receiver timing18 本地时钟 local clock复习资料二：专业英语填空练习一选择合适的答案填空（正确答案已在题中用“”表示）:1.Urgent communications which could not because of no reply one end of the link could have dramatic consequences. A. establish, in B. is established,

5、 with C. be establishing, to D. be established, at ()2.The operator of a local telephone switchboard had an option an optical or acoustical signal for the person over a wired network. A. transmit, search B. to transmit, searched () C. transmitting, searching D. to transmit, to search3.The operation

6、of a communication network needs a messaging system. A. to be complement with B. complement to C. to be complemented by () D. to complemented in4.Thus was born a new, but perpetually paging service as a one-way selective signaling system without speech. A. developing, defined () B. developed, defini

7、ng C. develop, define D. to develop, to define5.Today, certain models of pagers are even equipped with a display capability of optical messages of 10 to 80 characters. A. provide, consist B. provided, consisted C. providing, consisting () D. provision, consistant6.Paging systems using radio transmit

8、ters to this service remain currently in use mainly for service area not a few kilometers. A. dedicate, exceed B. dedicating, exceeded C. is dedicated, is exceeded D. dedicated, exceeding ()二选择合适的答案填空（正确答案已在题中用“”表示）:1.One of many reasons for a cellular mobile telephone system and it in many cities i

9、s the conventional mobile telephone system. A. develop, deploy B. to develop, to deploy C. developing, deploying () D. developed, deployed2.The ideal mobile telephone system would operate within a assigned frequency band and would serve an almost number of users in areas.A. limited, unlimited, unlim

10、ited ()B. limitation, limitation, limitationC. limit, limit, limitD. limiting,limiting, limiting3.LSI technology and mass production contribute to reduced cost in the future an average-income family should be able a mobile telephone unit. A. which, affording B. that, affordedC. when, afford D. so th

11、at, to afford ()4.Microprocessors and minicomputers are now for controlling many complicated features and functions with less power and size was previously possible. A. used, than () B. use, this C. using, they D. usage, it5.On Jan. 4, 1979, the FCC Illinois Bell Telephone Co. a developmental cellul

12、ar system in the Chicago area and make a limited offering of its cellular service to the public. A. authorize, conduct B. authorizing, conducting C. authorized, to conduct () D. to authorize, conducted6.Why 800 MHz? The FCCs decision 800 MHz was because of severe spectrum limitations at lower freque

13、ncy bands. A. to choose, made () B. choose, to make C. choice, make D. choice, making三选择合适的答案填空（正确答案已在题中用“”表示）：1.Computer data in the public domain by a packet switched data network X. 25 protocols.A. are transported, based on() B. transports, base onC. transported, based on D. to transport, base2.W

14、hen the future BISDN network, one must all possible existing and future services. A. design, take B. designing, take into account () C. designed, account D. to design, taking3.A telex network telex information, i. e. messages of characters, at very low speed. A. transports, transported () B. transpo

15、rted, transport C. to transport, to transport D. transporting4.The NISDN cannot transport TV signals its limited bandwidth capabilities, so a special TV network is still . A. because, require B. with, to require C. due to, required () D. within, requiring5.Each network is only capable one specific s

16、ervice for it was intentionally designed. A. of transporting, which () B. transporting, one C. transport, where D. to transport, when四.选择合适的答案填空（正确答案已在题中用“”表示）1.The telephone contains a transmitter and receiver for back and forth analog voice and analog electrical signals. A. convert, in B. converti

17、ng, between () C. conversion, to D. converted, into2.Each subscriber connecrs local loop to a switching center, as an end office.A. to, calling B. with, known C. the, know D. via, known ()3.The trunks are designed multiple voice-frequency circuits either FDM or synchronous TDM. A. carry, use B. carr

18、ied, used C. to carry, to use D. to carry, using ()4.Although originally to service analog telephone subscribers, the telephone network handles substantial data traffic modem, and gradually being converted to a digital network. A. implemented, via () B. implementing, in C. to implement, within D. de

19、sign, on5.Designers have found it convenient these nodes into a hierarchy or tree topology, five classes of switching centers or nodes. A. organization, consist B. organize, consisting C. to organize, consisting () D. organizing, to consist复习资料四：专业英语短文翻译1.The reader may ask , how does the demultiple

20、xer know which group of 8-digits relates to channel 1, 2, and so on ? Clearly this is important ! The problem is easily overcome by specifying a frame format , where at the start of each frame a unique sequence of pulses called the frame code , or synchronization word , is placed so as to identify t

21、he start of the frame. A circuit of the demultiplexer is arranged to detect the synchronization word, and thereby it knows that the next group of 8-digits corresponds to channel 1.2.Advances in audio, video and speech coding and compression algorithms and progress in Very Large System Integration te

22、chnology influence the bit rate generated by a certain service and thus change the service requirements for the network. In the future, new services with unknown requirement will appear. For the time being it is yet unclear, e. g. what the requirement in terms of bit rate for HDTV will be. A special

23、ized network has great difficulties in adapting to changing or new service requirements.3.When the transmitter wishes to send data, it first places the line in a space level (i. e. , the complement of a mark) for one element period. This element is called the start bit and has a duration of T second

24、s. The transmitter then sends the character, 1 bit at a time, by placing each successive bit on the line for a duration of T seconds, until all bits have been transmitted. Then a single parity bit is calculated by the transmitter and sent after the data bits. Finally, the transmitter sends a stop bi

25、t at a mark level (i. e. the same level as the idle state) for one or two bit periods. Now the transmitter may send another character whenever it wishes4.The cellular switch, which can be either analog or digital, switches calls to connect mobile subscribers to other mobile subscribers and to the na

26、tionwide telephone network. It also contains data links providing supervision links between the processor and the switch and between the cell sites and the processor. The radio link carries the voice and signaling between the mobile unit and the cell site. Microwave radio links or wire lines carry b

27、oth voice and data between the cell site and the MTSO.5.Today's telecommunication networks are characterized by specialization . This means that for every individual telecommunication service at least one network exists that transports this service. A few examples of existing public networks are

28、 described belowComputer data are transported in the public domain by a packet switched data network (PSDN) based on X.25 protocol6.Todays telecommunication networks are characterized by specialization . This means that for every individual telecommunication service at least one network exists that

29、transports this service. A few examples of existing public networks are described below: Computer data are transported in the public domain by a packet switched data network (PSDN) based on X.25 protocols. Television signals can be transported in three ways: broadcast via radio waves using ground an

30、tenna, by the coaxial tree network of the community antenna TV (CATV) network or recently via a satellite, using the so-called direct broadcast system (DBS)7.By far the most popular serial interface between a computer and its CRT (显示器) terminal is the asynchronous serial interface . This interface i

31、s so called because the transmitted data and the received data are not synchronized over any extended period and therefore no special means of synchronizing the clocks at the transmitter and receiver is necessary. In fact, the asynchronous serial data link is a very old form of data transmission sys

32、tem and has its origin in the era of theteleprinter.8.At the receiving end of an asynchronous serial data link, the receiver continually monitors the line looking for a start bit. Once the start bit has been detected, the receiver waits until the end of the start bit and then samples the next N bits

33、 at their centers, using a clock generated locally by the receiver. As each incoming bit is sampled, it is used to construct a new character. When the received character has been assembled, its parity is calculated and compared with the received parity bit following the character. If they are not eq

34、ual, a parity error flag is set to indicate a transmission error.9.If we consider binary transmission , the complete information about a particular message will always be obtained by simply detecting the presence or absence of the pulse. By comparison, most other forms of transmission systems convey

35、 the message information using the shape , or level of the transmitted signal ; parameters are most easily affected by the noise and attenuation introduced by the transmission path . Consequently there is an inherent advantage for overcoming noisy environments by choosing digital transmission.10. Th

36、e Internet is the largest repository of information which can provide very large network resources . The network resources can be divided into network facilities resources and network information resources . The network facilities resources provide us the ability of remote computation and communicat

37、ion . The network information resources provide us all kinds of information services , such as science , education , business , history , law , art , and , entertainment , etc11.The SDH standards are based on the principle of direct synchronous multiplexing which is the key to cost effective and fle

38、xible telecommunication networking. In essence, it means that individual tributary signals may be multiplexing directly into a higher rate SDH signal without intermediate stage of multiplexing. SDH Network Elements can then be interconnected directly with obvious cost and equipment savings over the

39、existing networks.1.读者也许会问，解复用器怎么知道哪一组8位码对应于第一路、第二路及其他各路呢?显然这是很重要的。我们只要指定一个帧格式，这个问题就容易解决了。在一个帧格式里，在每一帧的开始放置一个称为帧码或同步字的独特的码序列，以标志每帧的开始，而用解复用器的一个电路去监测同步字，从而它知道下一个8为码组对应话路1。2.在声音、图像、语声编码和压缩算法以及在特大系统综合（VLSI）技术方面的进步影响着一定业务的比特率，因而改变着对网络的业务要求。在将来，未知需求的新业务将会出现。例如HDTV（高清晰度TV）将在比特率上有何要求当前仍不清楚。一个专用化网络在适应变化和新业务

40、要求方面具有极大困难。3.当发送器想要发送数据时，它首先将线路置成空号电平（即信号的反码），此电平持续一个单元（码元）的间隔时间。此（空号）单元称为起始位，持续时间为T 秒。然后发送器发送字符，一次一个比特地将相继的码元送上线路。每个码元持续T 秒，直到所有码元发完为止。此后，发送器计算得出一个奇遇校验位并将它在数据码元之后发出。最后，发送器送出一个停止位，其电平为信号电平（与空闲状态电平相同），时长为1个或2个比特宽度。如果发送器需要，它又可发送另一个字符。4.蜂窝交换机即可以是模拟的也可以是数字的，它对移动用户之间和移动用户与全国电话网之间的呼叫进行交换连接。它还有在处理机与交换机间和在无

41、线基地站与处理机间起监控作用的数据线。无线线路在移动机和无线基地站间传输话音和信令。微波无线线路或有线线路在无线基地站和移动电话交换局之间传送音频信号和数据信号。5、6.当前电信网络的特征是专用化，即对每一种电信业务，至少有一个传送该业务网络存在。下面列举了当今几个公用网的例子。计算机的数据在公众域中是在以X.25协议为基础的分组交换数据网（PSDN）中传送，而在有限的数个国家，它是在X.21协议为基础的电路交换数据网中传送的。电视信号可以三种方式传送：利用地面天线，通过无线广播；由公共天线TV（CATV）同轴电缆树形网络传送；近来，人们又利用称为直接广播系统（DBS）经卫星进行传送。7.在计

42、算机及其显示终端之间最为常见的串行接口是异步串行接口。这个接口之所以如此称呼，是因为无论在多长的时间区间里发送的数据和接收的数据是不同步的，因而没有必要采用特殊的手段使发送器和接收器的时钟同步。实际上，异步串行数据链路是一种古老的数据传输方式，它起源于电传打字机的时代。8.在异步串行数据链路系统的接收端，接收器持续监视着线路，搜索着起始位。一旦检测到起始位并等到它结束，接收器就对随后的N个码元抽样，抽样点选在这些码元的中心处。抽样所用的时钟是由接收器本地产生的。当每一个输入的码元被抽样后，就用这些码元构成一个新的字符。当接收到的字符汇齐后，它的奇偶校验位就由计算得出并与接收到的奇偶校验位进行比

43、较。如果它们不等，则将奇偶校验错误标志置位，以标明传输错误。9.研究二进制信号的传输可见，只要简单地去判别脉冲的“有”和“无”，我们就获得了一条消息的全部信息。相比之下，许多其他形式的传输系统是利用被传信号的波形或电平的高低来传送信息的，而这些参数有极易受到传输途径中的噪声和衰耗的影响。因此选择数字传输系统在克服噪声环境的影响方面有其固有的优势。10.Internet是最大的信息宝库，它可以提供非常巨大的网络资源。这种网络资源可分为网络设备资源和网络信息资源。网络设备资源使我们能够进行远程计算和通信。网络信息资源向我们提供各种各样的信息服务，如科学、教育、商务、历史、法律、艺术和娱乐等等。11

44、.SDH标准的基础是直接同步复用。这一原理是低价高效和灵活组网的关键。从本质上讲，这意味着各支路信号可以被直接复用到更高速率的SDH信号之中，而用不着中间级的复用阶段。诸SDH网络单元可以直接相互连接，因而显然比现在的网络更省钱、更省设备。 复习资料五：专业英语句子翻译UNIT 1(1) Practical equipments, however, normally use a sampling rate of 8 kHz, and if 8-digits per sample value7 are used, the voice channel becomes represented by

45、a stream of pulses with a repetition rate of 64 kHz. (2) It is the relationship of the true signal to the noise signal, known as the signal-to-noise ratio10, which is of the most interest to the communication engineer. (3) Alternative examples may be found within terrestrial systems where, although

46、the message signal is strong, so is the noise power. (4) So far in this discussion we have assumed that each voice channel has a separate coder, the unit that converts sampled amplitude values to a set of pulses; and decoder, the unit that performs the reverse operation.UNIT 2 (1) This interface is

47、so called because3 the transmitted data and the received data are not synchronized over any extended period and therefore no special means of synchronizing the clocks at the transmitter and receiver is necessary. (2) The fundamental problem encountered by all serial data transmission systems is how

48、to split the incoming data stream into individual units (i. e. , bits) and how to group these units into characters. (3) These characters are invariable units comprising 7 or 8 bits of “information” plus 2 to 4 control bits11 and frequently correspond to ASC11-encoded characters. (4) The transmitter

49、 then sends the character, 1 bit at a time, by placing each successive bit on the line for a duration of T seconds, until all bits have been transmitted. (5) When the received character has been assembled, its parity is calculated and compared with the received parity bit following the character. (6

50、) Suppose the receiver clock waits T/2 seconds from the falling edge of the start bit and samples the incoming data every T seconds thereafter until the stop bit has been sampled.UNIT 4 (1) The original idea was to increase computing capacity that could be shared by users in many locations and to fi

51、nd out what it would take for computer networks to survive a nuclear war or other disaster by providing multiple path between users. People on the ARPNET quickly discovered that they could exchange messages and conduct electronic “conferences” with distant colleagues for purposes that had nothing to

52、 do with the military industrial complex. (2) What you need to know is that you can exchange message with other computers on the internet and use your computer as a remote terminal on distant computers. (3) Not only should the users know where the resources locate, but also he should know some opera

53、ting commands concerned. (4) For example, somebody would ask a question in a conference, and a complete stranger would send back an answer: after the same questions were repeated several times by people who hadnt seen the original answers, somebody else gathered a list of “frequently asked questions

54、” and placed it where newcomers could find it.UNIT 8 (1) Any communication system which can provide customers with means to communicate from any place, at any time and at any distance gives social and economic advantages. (2) Urgent communications (police, firemen, hospitals, etc.) which could not b

55、e established because of no reply at one end of the link could have dramatic consequences if the delay in response is too long or if the call remain unanswered. (3) The operation of a communication network needs, for this reason, to be complemented by a messaging system (one-way or two-way) which can offer either an additional facility in the case of a sophisticated network or a primary communic