高级通信工程师考试复习题

通信英语强化训练试题（一）Ⅰ单项选择题：(Choose the best one)( )1.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. convey, to occupy( )2.For example, the signal _________from a satellite, _________in far outer space, is very weak.A. received, locatedB. receive, locateC. receiving, locatingD. to receive, to locate( )3.If we consider binary transmission, the complete information about a particular message will always _________by simply _________the presence or absence of the pulse.A. obtain, detectB. be obtained, detectingC. obtained, detectedD. obtaining, detected( )4. 4. There is an inherent advantage for _________noisy environments by _________digital transmission.A. overcoming, chooseB. overcome, choosingC. overcome, chooseD. overcoming, choosing( )5.Each voice channel has a separate coder，the unit _________converts sampled amplitude values to a set of pulses; And decoder, the unit _________performs thereverse operation.A. who, whoB. when, whenC. where, whereD. that, that( )6.The problem is easily overcome by _________a frame format, where at the start of each frame a unique sequence of pulses is placed _________the start of the frame.A. specify, identifyB. specifying, so as to identifyC. specified, identifiedD. specify, identifying( )7.An asynchronous serial data link is said _________character oriented，as information is transmitted in the form of groups of bits _________characters.A. be，callingB. to being，to callC. been，callD. to be，called( )8.This interface is so called because the _________data and the _________data are not synchronized over any extended period.A. transmit，receiveB. to transmit，to receiveC. transmitting，receivingD. transmitted，received( )9.Serial data transmission systems _________in the telephone，Morse code, and even the smoke signals once _________by native Americans.A. are finding，usingB. are found，usedC. find, useD. be found, using( )10.Traditionally，the idle state _________the mark level. By convention this corresponds _________a logical 1 level.A. is referred to, asB. is referred as, inC, is referred to as, to D. is referred，within( )11.The transmitter then sends the character，1 bit at a time，by _________each successive bit on the line for a duration of T seconds, _________all bits have beentransmitted.A. place, stillB. placed，sinceC. placing, untilD. placing，because( )12.When the data link connects a CRT terminal _________a computer，_________problems arise, as the terminal is itself character oriented.A. into, manyB. on，a fewC. in, a fewD. to，few( )13._________the receiving end of a synchronous serial data link，the receiver continually 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 _________networking technology, they added networks and expanded_________networks almost as rapidly as new 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 occur at each layer. More importantly, the OSI reference model is a framework you canuse _________how information travels throughout a network.A. view, understandB. viewing, understandingC. viewed, understoodD. to view, to understand( )16.The transport layer segments data from the _________host’s system and reassembles the data into a data stream on the _________host’s system.A. sending, receivingB. to send, to receiveC. sent, receivedD. send, receive( )17.The data link layer provides the transit of data _________a physical link. In so doing, the data link layer is concerned _________physical addressing, networktopology, network media access, and error detection.A. with, acrossB. at, inC. between, inD. across, withⅡ短语英译汉：(Translate the following phrases into Chinese)1.the schemes for performing these three functions2. a series of amplitude values3. a speech channel of telephone quality4. a sequence of 8-binary digits5. a minimum theoretical sampling frequency6. a voice channel occupying the range 300 Hz to 3. 4 kHz7.8-digits per sample value8.the sparking of a car ignition system9.the stream 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 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 system19.the presence or absence of the pulse20. a high-speed electronic switch21.the time division multiplexer22.Time Division 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 characters31.the invariable units comprising 7 or 8 bits of information32. a clock generated locally by the receiver33.the received parity bit following the character34.the falling edge of the start bit35.the character-oriented nature of the data linkworking technology37.proprietary networking system38.the International Organization for Standardizationpatibility between the various types of networks40.seven numbered layers41.standardization of network components42.error recovery43.receiving host's system44.connection-oriented circuitsrmation flow controlwork topologywork media access48.electrical specification49.maximum transmission distanceⅢ短语汉译英：(Translate the following phrases into English)1.抽样量化与编码2.话路3.幅值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27.发送器与接收器28.数据传输29.数据流30.闲置状态31.传号电平32.空号电平33.起始位34.停止位35.T秒的持续时间36.奇偶校验位37.错误标志38.传输错误39.下降沿40.符号间的空格41.接收机的定时42.本地时钟43.磁带44.控制比特45.逻辑1电平46.二进制数据47.明显的缺点48.联网技术49.国际标准化组织50.参考模型51.数据分组52.应用程序53.网络媒体54.分层55.硬件和软件56.表示层57.传输层58.数据链路层59.网络服务60.文件接入61.数据格式62.主机63.协议64.连接65.逻辑选址Ⅳ请将下述短文译成中文（短文英译汉）：(Translate the following passages into Chinese)1.If we consider binary transmission, the complete information about a particular messagewill always be obtained by simply detecting the presence or absence of the pulse. By comparison, most other forms of transmission system convey the message information using the shape, or level of the transmitted signal; parameters that 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.2.The reader may ask, how does the demultiplexer know which group of 8-digits relates tochannel 1, 2, and so on? Clearly this is important! The problem is easily overcome by specifyinga frame format, where at the start of each frame a unique sequence of pulses called the framecode, or synchronization word, is placed so as to identify the 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 1.3.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 low-level noise within the communication equipment itself. It is the relationship of the true signal to the noise signal, known as the signal-to-noise ratio, which is of most interest to the communication engineer.4.Basically, if the signal is very large compared to the noise level, then a perfect message can take place; however, this is not always the case. For example, the signal received from a satellite, located in far outer space, is very weak and is at a level only slightly above that of the noise. Alternative examples may be. Found within terrestrial systems where, although the message signal is strong, so is the noise power.5.So far 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. This need not be so, and systems are in operation where a single codes is shared between 24, 30, or even 120 separate channels.6. A high-speed electronic switch is used to present the analog information signal of each channel, taken in turn, to the codec. The codec is then arranged to sequentially sample the amplitude value, and code this value into the 8-digit sequence. Thus the output to the codec may be seen as a sequence of 8 pulses relating to channel 1, then channel 2, and so on. This unit is called a time division multiplexer.7.An asynchronous serial data link is said to be character-oriented, as information is transmitted in the form of groups called characters. These characters are invariable units comprising 7 or 8 bits of information plus 2 to 4 control bits and frequently correspond to ASCII-encoded characters. Initially, when no information is being transmitted, the line is in an idle state. The idle state is referred to as the mark level and corresponds to a logical 1 level.8.When the transmitter wishes to send data, it first places the line in a space level for one element period. 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 bit at a mark level for one or two bit period.9.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 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.10.The most obvious disadvantage of asynchronous data transmission is the need for a start, parity, and stop bit for each transmitted character. If 7 bit characters are used, the overall efficiency is only 70 percent. A less obvious disadvantage is due to the character-oriented nature of the data link. Whenever the data link connects a CRT terminal to a computer, few problems arise, as the terminal is itself character oriented.11.The most critical aspect of the system is the receiver timing. The falling edge of the start bit triggers the receiver's 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 the incoming data every T seconds thereafter until the stop bit has been sampled. As the receiver's clock is not synchronized with the transmitter clock, the sampling is not exact.12.By far the most popular serial interface between a computer and its CRT terminal is the asynchronous serial interface. This interface is 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 system and has its origin in the era of the teleprinter.13.Most computer terminals transmit and receive ASCII characters, and we know that the ASCII characters require 7 bits. Therefore, 7 bits of data plus a parity bit are sent each time a character is transmitted or received by the terminal. The two most obvious ways to send the characters are by parallel transmission or by serial transmission. Most terminals have been designed to transmit and receive ASCII characters as serial data.14.The early development of LANs, MANs, and W ANs was chaotic in many ways. The early 1980s saw tremendous increases in the numbers and sizes of networks. As companies realized they could save money and gain productivity by using networking technology, they added networks and expanded existing networks almost as rapidly as new network technologies and products could be introduced.15.Proprietary systems are privately developed, owned, and controlled. In the computer industry, proprietary is the opposite of open. Proprietary means that one or a small group of companies controls all usage and evolution of the technology. Open means that free usage of the technology is available to the public.16.The OSI reference model allows you to view the network functions that occur at each layer. More importantly, the OSI reference model is a framework you can use to understand how information travels throughout a network. In addition, the OSI reference model can be used to visualize how information, or data packets, travels from application programs, through a network medium, to other application programs that are located in another computer on a network, even if the sender and the receiver have different types of network media.17.The application layer is the OSI layer that is closest to the user. It provides network services, such as file access and printing, to the user’s applications. It differs from the other layers in that it does not provide services to any other OSI layer, but rather, only to applications outside the OSI model. The application layer establishes the availability of intended communication partners. It also synchronizes and establishes an agreement on procedures for error recovery and control of data integrity.18.The transport layer attempts to provide a data transport service that shields the upper layers from transport implementation details. Specifically, such issue as how reliable transport between two hosts is accomplished in the concern of the transport layer. In providing communication service, the transport layer establishes, maintains, and properly terminates connection-oriented circuits. In providing reliable service, transport errordetection-and-recovery and information flow control are used.19.The physical layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between end systems. Such characteristics as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other, similar, attributes are defined by physical layer specifications.Ⅴ阅读理解：(True or false statement) According to the following text's decide whether the statements following the texts are true (T) or false (F)PASSAGE ONEDigital transmission provides a powerful method for overcoming noisy environments. Noise can be introduced into transmission path in many different ways: perhaps via a nearby lightning strike, the sparking of a car ignition system, or the thermal low-level noise within the communication equipment itself. It is the relationship of the true signal to the noise signal, known as the signal-to-noise ratio, which is of the most interest to the communication engineer. Basically, if the signal is very large compared to the noise level, then a perfect message can take place; however, this is not always the case. For example, the signal received from a satellite, located in far outer space, is very weak and is at a level only slightly above that of the noise. Alternative examples may be found within terrestrial systems where, although the message signal is strong, so is the noise power.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 the message information using the shape, or level of the transmitted signal; parameters that 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.( )1.If the true signal is very large compared to the noise level, then the information with higher quality can be obtained.( )2.If we consider binary transmission, the complete information about a particular message will always be obtained by detecting the shape of the transmitted signalor by calculating the parameters of the transmitted signal.( )3.It is the signal-to-noise ratio which is of the most interest to the communication engineer.( )4.Digital transmission provides the signal-to-noise ratio, which is a very important parameter, for overcoming noisy environments.( )5.The signal gotten from a satellite is generally very weak.( )6.The shape of the transmitted signal are most easily affected by the noise and attenuation introduced by the codec.PASSAGE TWOSo far 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. This need not be so, and systems are in operation where a single codec (i.e., coder and its associated decoder) is shared between 24, 30, or even 120 separate channels. A high-speed electronic switch is used to present the analog information signal of each channel, taken in turn, to the codec. The codec is then arranged to sequentially sample the amplitude value, and code this value into the 8-digit sequence. Thus the output, to the codec may be seen as a sequence of 8 pulses relating to channel 1, then channel 2, and so on. This unit is called a time division multiplexer (TDM). The multiplexing principle that is used is known as word interleaving. Since the words, or8-digit sequences, are interleaved in time.At the receive terminal a demultiplexer is arranged to separate the 8-digit sequences into the appropriate channels. The reader may ask, how does the demultiplexer 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 the 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. The synchronization word reoccurs once again after the last channel has been received.( )7.At the receive terminal the reverse operation to the multiplexing is needed to separate the 8-digit sequences into the appropriate channels.( )8.The codec in the transmitting terminal is to sample the amplitude value, and code this value into the 8-digit sequence.( )9.The demultiplexer knows which group of 8-digits relates to channel 1 as soon as it finds the synchronization word.( )10.From above text, we understand each voice channel has a coder.( )11.The time division multiplexer is so called since there is a special word called synchronization word.( )12.He group of 8-digits following the synchronization word relates to chart e1 1.PASSAGE THREEBy far the most popular serial interface between a computer and its CRT terminal is the asynchronous serial interface. This interface is 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 system and has its origin in the era of teleprinter.An asynchronous serial data link is said to be character-oriented, as information is transmitted in the form of groups of bits called characters. These characters are invariable units comprising 7 or 8 bits of "information" plus 2 to 4 control bits and frequently correspond to ASCII-encoded characters.The most critical aspect of the system is the receiver timing. The falling edge of the start bit triggers the receiver's local clock, which samples each incoming bit at its nominal center. 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. As the receiver's clock is not synchronized with the transmitter clock, the sampling is not exact.The most obvious disadvantage of asynchronous data transmission is the need for a start, parity, and stop bit for each transmitted character. If 7 bit characters are used, the overall efficiency is only 70%. A less obvious disadvantage is due to the character-oriented nature of the data link. Whenever the data link connects a CRT terminal to a computer, few problems arise, as the terminal is itself character oriented. However, if the data link is being used to, say, dump binary data to a magnetic tape, problems arise.( )13.The most obvious disadvantage of asynchronous data transmission is about the lower transmission efficiency.( )14.In fact, the asynchronous serial data link is the teleprinter.( )15.The falling edge of the start bit triggers the receiver's local clock, which samples each bit sent from the transmitter.( )16.From above text we understand the characters are variable units.( )17.For each transmitted character, a start, parity, and stop bit are needed.( )18.Special means is needed to synchronize the clocks at the transmitter and receiver.PASSAGE FOURAn asynchronous serial data link is said to be character-oriented, as information is transmitted in the form of groups of bits called characters. These characters are invariable units comprising 7 or 8 bits of "information" plus 2 to 4 control bits and frequently correspond to ASCII-encoded characters. Initially, when no information is being transmitted, the line is in an idle state. Traditionally, the idle state is referred to as the mark level. By convention this corresponds, to a logical l level.When the transmitter wishes to send data, it first places the line in a space level (1.e., the complement of a mark) for one element period. This element is called the start bit and has duration of T seconds. The transmitter then sends the character, 1 bit at a time, by placing each successive bit on the line for 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 bit 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 wishes.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 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 equal, a parity error flag is set to indicate a transmission error.( )19.An asynchronous serial data link is said to be character oriented, because a duration of T seconds is needed for each character.( )20.When the transmitter wishes to send data, it first places the line in logical 0 level. ( )21.At the receiving terminal a single parity bit is calculated by the transmitter and compared with the received parity bit.( )22.At the receiving end of an asynchronous serial data link, the receiver continually monitors the line to search the start bit.( )23.The receiver samples the bits sent from the transmitter using characters generated by the receiver.( )24.If the parity bit calculated by the receiver is not equal to the received one, transmission error occurs.。