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Digital data can also be represented by (71)signals by use ofa modem. The modem converts a series of binary voltage (72) into an analog signal by encoding the digital data ontoa carrier frequency. The resulting signal occupies a certam spectrum of (73) ce

题目

Digital data can also be represented by (71)signals by use ofa modem. The modem converts a series of binary voltage (72) into an analog signal by encoding the digital data ontoa carrier frequency. The resulting signal occupies a certam spectrum of (73) centered about the carTier and may be propagated acrossa medium suitable for that carrier. The most common modems represent digital data in the voice(74)and hence allow those datato be propagated over ordinary voice-grade (75 )lines At the other end of the line, another modem demodulates the signal to recover the original data

(71)

A.analog

B.digital

C.Modem

D.electric

相似考题

1.Not only () the data fed into it, but it can also analyze them.A.the computer can memorizeB.can the computer memorizeC.do the computer memorizeD.can memorize the computer

2.Telecommunications stand for devices and systems that transmit electronic or optical signals across long distances. Telecommunications enables people around the world to contact one another, to access information instantly, and to communicate from remote areas. Telecommunications usually involves a sender of information and one or more recipients linked by a technology, such as a telephone system, that transmits information from one place to another. Telecommunications enables people to sand and receive personal messages across town, between countries, and to and from outer space. It also provides the key medium for delivering news, data, information, and entertainment.Telecommunications devices convert different types of information, such as sound and video, into electronic or optical signals. Electronic signals typically travel along a medium such as copper wire or are carried over the air as radio waves. Optical signals typically travel along a medium such as strands of glass fibers. When a signal reaches its destination, the device on the receiving end converts the signal back into an understandable message, such as sound over a telephone, moving images on a television, or words and pictures on a computer screen.Telecommunications messages can be sent in a variety of ways and by a wide range of devices. The messages can be seat from one sender to a single receiver (point-to-point) or from one sender to many receivers (point-to-multipoint). Personal communications, such as a telephone conversation between two people or a facsimile (fax) message (see Facsimile Transmission), usually involve point-to-point transmission. Point-to-multipoint telecommunications, often called broadcasts, provide the basis for commercial radio and television programming.Telecommunications begin with messages that are converted into electronic or optical signals. Some signals, such as those that carry voice or music, are created in an analog or wave format, but may be converted into a digital or mathematical format for faster and more efficient transmission. The signals are then sent over a medium to a receiver, where they are decoded back into a form. that the person receiving the message can understand. There are a variety of ways to create and decode signals, and many different ways to transmit signals.Individual people, businesses, and governments use many different types of telecommunications systems. Some systems, such as the telephone system, use a network of cables, wires, and switching stations for point-to-point communication. Other systems, such as radio and television, broadcast radio signals over the air that can be received by anyone who has a device to receive them. Some systems make use of several types of media to complete a transmission. For example, a telephone call may travel by means of copper wire, fiber-optic cable, and radio waves as the call is sent from sender to receiver. All telecommunications systems are constantly evolving as telecommunications technology improves. Many recent improvements, for example, offer high-speed broadband connections that are needed to send multimedia information over the Internet.Personal computers have pushed the limits of the telephone system as more and more complex computer messages are being sent over telephone lines, and at rapidly increasing speeds. This need for speed has encouraged the development of digital transmission technology. The growing use of personal computers for telecommunications has increased the need for innovations in fiber-optic technology.Telecommunications and information technologies are merging and converging. This means that many of the devices now associated with only one function may evolve into more versatile equipment. This convergence is already happening in various fields. Some telephones and pagers are able to store not only phone numbers but also names and personal information aboA．Current development.B．Transmission of message.C．Computer networking.D．Government regulation.

3.What can be concluded about "modem" ?A．It converts data from one form. to another.B．It will be out of date soon.C．It serves as a link between senders and recipients of message.D．It transmits message more efficiently than other devices.

4.●One use of networks is to let several computers share (71) such as file systems，printers，and tape drives.(71) A．CPUB．memoryC．resourcesD．data

更多“Digital data can also be represented by (71)signals by use ofa modem. The modem converts a ”相关问题

  • 第1题：

    Because Web servers are platform. and application(71)，they can send or request data from legacy or external application including database．All replies，once converted into(72)mark up language，can then be transmitted to a(73)．Used in this way，Intranets can(74)lower desktop support costs，easy links with legacy application and databases and，(75)all。ease of use．

    (74)

    A．coupled

    B．dependent

    C．independent

    D．related


    正确答案：C

  • 第2题：

    As a network administrator, you will need to decide on the appropriate network devices to use. Which of the following correctly describes the roles of devices in a WAN? (Choose three)

    A. A CSU/DSU terminates a digital local loop.

    B. A router is commonly considered a DCE device.

    C. A modem terminates an analog local loop.

    D. A router is commonly considered a DTE device.

    E. A modem terminates a digital local loop.

    F. A CSU/DSU terminates an analog local loop.

    G. A modem is used to terminate a T1


    正确答案：ACD
    A,C,D

  • 第3题：

    An analog signal's characteristic quantity representing data may 66). at any instant, any value within a continuous(67). For example, an analog signal may follow continuously the values of another physical quantity representing data.A discrete signal is composed of(68)elements in time, each element having one or more characteristic quantities which can represent data. Examples of characteristic quantities are amplitude, waveform,(69), and position in time. A digital signal is a special case of discrete signals, in which data are represented by a(70)number of well-defined discrete values that one of its characteristic quantities may take in time.

    A．acquire

    B．collect

    C．assume

    D．fetch


    正确答案：C

  • 第4题：

    Soon, more of the information we receive via the Internet could come(71)in digital wrappers.

    Wrappers are made up(72)software code that's targeted to do specific things with the data(73)within them, such as helping to define queries for search engines. They also keep(74)from(75)access to that code.

    A．package

    B．packaged

    C．packages

    D．packaging


    正确答案：B

  • 第5题：

    共用题干
    Computers in Cars
    You're far from home on a lonely road.Shadowy forests stretch away on both sides.A thick mist（雾）makes it difficult to see far beyond your car's windshield（挡风玻璃）.
    “Can this be route 90A?”you wonder. if it is,you should be near a town.Yet there's no hint of one .Night is closing in.And you're low on gasoline.
    This is a situation where an in-car computer that can navigate would be a big help.
    A car computer that navigates?Yes!Such computers exist.Several experimental models are being tested by General Motors,Ford,Chrysler,and several foreign car makers.These computers vary in detail .But they all contain series of maps on videodiscs or videotapes.For example,one computer system contains 13,300 maps covering the continental US.
    Before starting out on a trip,a driver can type in the code for the region he or she plans to drive through .The computer then shows a map of that region.At the same time,a tiny radio re-ceiver linked to the computer goes to work.It picks up signals from navigation satellites such as the NAVSTAR network.Using these signals,the computer shows the car's position at all times and displays this position on the map.The computer can also calculate and display the best route to follow.
    A navigation computer may also receive and use data about road construction,weather condi- tions,and traffic jams.This information would be displayed to the driver and the computer would also use the information to work out alternate（交替的）routes.
    Most cars nowadays also contain computers that help cars run more efficiently .Microproces- sors（微处理机）control certain engine functions by regulating the mixing of fuel. Data on car speed,oil pressure,revolutions per minute,engine temperature,and fuel level can be displayed as digital data(numbers)or warning lights.
    Some auto designers suggest that a central computer display be used to clearly present such timely information as car speed and fuel level.Warning lights would indicate a drop in oil pres- sure or a sudden rise in engine temperature .To get more information on these conditions,the driver could call it up on the computer display screen.When needed,the computer could be “asked”to provide navigation aid or information about the car's condition.

    The navigation computers have one thing in common:they all______.
    A: contain series of maps on videodiscs or videotapes
    B: contain 13,300 maps covering the continental US
    C: can be obtained free of charge
    D: cost a lot of money

    答案：A
    解析：
    文章第二段描述了一位司机迷路的情况，紧接着第三段讲到，当汽车上装载了计算机导航系统后，会给司机带来很大的方便。很明显，答案为选项C。
    本题属于词汇题，问“navigate”在第三段中的意思是什么？navigate的本意是“导航”，即选项C的意思，但在文中，它不是给轮船导航，而是为汽车导航，为驾驶员指路，故选项B为正确答案。
    本题是根据第四段中间这两句话出的问题：These computers vary in detail. But they all contain series of maps on videodiscs or videotapes．所有（车载）计算机导航系统都含有电子地图，即保存在视盘或录像带上的地图（series of maps on videodiscs or videotapes),所以A为正确答案。
    本题问题的是当车载计算机收不到来自导航卫星的信号时会出现什么情况。根据常识可以判断，计算机无法确定汽车的位置。此题可以通过第五段中的“Using these signals,the computer shows the car's position at all times and displays this position on the map.”推断出来：本题是此句意思的反说。
    选项中给出了计算机导航系统的几个功能，问其中哪项不是。通过阅读短文，我们发现选项B的信息文中没有提到，故此题选B。

  • 第6题：

    Which two statements are true about analog to digital conversion of voice signals for use in digital telephony networks？（）

    • A、The three required steps in the analog to digital conversion are sampling，encoding，and compression.
    • B、The three required steps in the analog to digital conversion are sampling，quantization，and compression.
    • C、The three required steps in the analog to digital conversion are sampling，quantization，and encoding.
    • D、The output of the sampling process is a pulse code modulation （PCM） signal.
    • E、The output of the sampling process is a pulse amplitude modulation （PAM） signal.

    正确答案:C,E

  • 第7题：

    When a router converts analog signals to digital signals， what three steps are always included in the process？（）

    • A、involution
    • B、encoding
    • C、sampling
    • D、quantization
    • E、compression
    • F、companding

    正确答案:B,C,D

  • 第8题：

    Which benefit does digital subscriber line (DSL) systems for broadband access provide to the user?（）

    • A、Secure access to company extranet
    • B、Dedicated lines for high security data transfer
    • C、Simple solution for high-quality digital video using coaxial cable
    • D、Data and audio signals that share the same communications infrastructure

    正确答案:D

  • 第9题：

    Which test checks the transmitter and receiver of a local modem？（）

    • A、data parity
    • B、analog loop back
    • C、local digital loop back
    • D、remote digital loop back

    正确答案:B

  • 第10题：

    多选题
    Which two statements are true about analog to digital conversion of voice signals for use in digital telephony networks？（）
    A

    The three required steps in the analog to digital conversion are sampling，encoding，and compression.

    B

    The three required steps in the analog to digital conversion are sampling，quantization，and compression.

    C

    The three required steps in the analog to digital conversion are sampling，quantization，and encoding.

    D

    The output of the sampling process is a pulse code modulation （PCM） signal.

    E

    The output of the sampling process is a pulse amplitude modulation （PAM） signal.


    正确答案： B,E
    解析： 暂无解析

  • 第11题：

    多选题
    When a router converts analog signals to digital signals， what three steps are always included in the process？（）
    A

    involution

    B

    encoding

    C

    sampling

    D

    quantization

    E

    compression

    F

    companding


    正确答案： E,F
    解析： 暂无解析

  • 第12题：

    单选题
    Which benefit does digital subscriber line (DSL) systems for broadband access provide to the user?（）
    A

    Dedicated lines for high security data transfer

    B

    Data and audio signals that share the same communications infrastructure

    C

    Secure access to company extranet

    D

    Simple solution for high-quality digital video using coaxial cable


    正确答案： B
    解析： 暂无解析

  • 第13题：

    ●Users also need (71) systems to help them explore the web and discover interesting data sources and interfaces that support different query and search paradigms.

    (71) A．negative

    B．adaptive

    C．passive

    D．adaption


    正确答案：B
    【解析】用户也需要适应性的系统以帮助他们探索网络、发现支持不同查询和搜索范例的有趣数据源和界面。

  • 第14题：

    Digital computer is controlled by internally stored programs and(66) of using common storage for all or part of a program and also for all or part of the data necessary for the execution of the programs; executing user-written or user-designated programs; performing user-designated manipulation of digitally represented discrete data, including.(67) operations and logic operations; and executing programs that(68) themselves during their execution.Analog computer's operations are analogous to the(69) of another system and that accepts, processes, and produces analog data.(70) computer integrates analog computer components and digital computer components by interconnection of digital-to-analog converters and analog-to-digital converters.

    A．qualified

    B．competent

    C．capable

    D．able


    正确答案：C

  • 第15题：

    is a device that converts images to digital format．

    A．Copier

    B．Printer

    C．Scanner

    D．Display


    正确答案：C

  • 第16题：

    Because Web servers are platform. and application(71)they can send or request data from legacy or external applications including databases. All replies, once converted into(72)mark-up language, can then be transmitted to a(73). Used in this way, Intranets can(74)lower desktop support costs, easy links with legacy applications and databases and,(75)all, ease of use.

    A．related

    B．dependent

    C．coupled

    D．independent


    正确答案：D

  • 第17题：

    DDN是（）的缩写。

    • A、Digital Data Net
    • B、Digital Data Network
    • C、Digital Date Net
    • D、Digital Date Network

    正确答案:B

  • 第18题：

    Which three functions are associated with a Cisco Unified CallManager？ （）

    • A、 connects traditional telephony devices to voice over IP infrastructure
    • B、 converts analog signals to digital format
    • C、 performs voice compression
    • D、 performs call processing
    • E、 performs dial plan administration
    • F、 performs signaling and device control

    正确答案:D,E,F

  • 第19题：

    What is the difference between a CSU/DSU and a modem?（）

    • A、A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line
    • B、A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line
    • C、A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line
    • D、A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line

    正确答案:D

  • 第20题：

    What is the difference between a CSU/DSU and a modem?（）

    • A、A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line.
    • B、A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line.
    • C、A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line.
    • D、A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line.

    正确答案:D

  • 第21题：

    You need to design the network to support the company’s VPN requirements for mobile users who connect to the network in Seattle. Which two actions should you perform？（）

    • A、Use a password generator application to create a preshared key， and distribute it to all mobile users
    • B、Use computer autoenrollment to create digital certificates that can be used to authenticate to a VPN server
    • C、Acquire a digital certificate that can be used for SSL from a commercial CA for each computer that established a VPN connection
    • D、Configure IPSec policies on all Routing and Remote Access servers to require the use of digital certificates

    正确答案:B,D

  • 第22题：

    单选题
    What is the difference between a CSU/DSU and a modem?（）
    A

    A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line

    B

    A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line

    C

    A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line

    D

    A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line


    正确答案： C
    解析： 暂无解析

  • 第23题：

    单选题
    What is the difference between a CSU/DSU and a modem？（）
    A

    A CSU/DSU converts analog signals from a router to a leased line; a modem converts analog signals from a router to a leased line.

    B

    A CSU/DSU converts analog signals from a router to a phone line; a modem converts digital signals from a router to a leased line.

    C

    A CSU/DSU converts digital signals from a router to a phone line; a modem converts analog signals from a router to a phone line.

    D

    A CSU/DSU converts digital signals from a router to a leased line; a modem converts digital signals from a router to a phone line.


    正确答案： A
    解析： 暂无解析

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