计算机英语Unit计算机通信课件.ppt

计算机英语Unit计算机通信第1页，此课件共37页哦Unit 7 Computer CommunicationsSection A Telecommunications and Computer第2页，此课件共37页哦第七单元：计算机通信课文A：电信与计算机第3页，此课件共37页哦 Telecommunications allows 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 devices converts different types of information,such as sound and video,into electronic signals.The signals can then be transmitted by means of media such as telephone wires or radio waves.第4页，此课件共37页哦电信使世界各地的人们得以互相联系，即刻获取信息，并从边远地区实施通信。电信通常涉及一个信息发送者和一个或多个接收者，他们通过电话系统等把信息从一地发送到另一地的技术相联系。电信设备将不同类型的信息，如声音和图像，转换成电子信号。然后，这些信号就可以通过电话线或无线电波等媒介进行发送。第5页，此课件共37页哦 When a signal reaches its destination,the device on the receiving end converts the electronic 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 enable people to send and receive personal messages across town,between countries,and to and from outer space.It also provides the key medium for news,data,information,and entertainment.第6页，此课件共37页哦信号到达目的地后，接收端的设备将电子信号转换回可以理解的信息，如电话中的声音、电视上的活动图像或计算机屏幕上的文字和图片。电信使人们能够在城镇不同地方、国家之间以及向外层空间和从外层空间发送和接收个人信息。电信也为新闻、数据、信息和娱乐提供了关键的媒介。第7页，此课件共37页哦 Telecommunications messages can be sent in a variety of ways and by a wide range of devices.The messages can be sent 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,usually involve point-to-point transmission.Point-to-multipoint telecommunications often called broadcasts,provide the basis for commercial radio and television programming.第8页，此课件共37页哦电信信息可通过各种方式和设备发送。信息可由一个发送者发送给一个接收者（点对点），或者由一个发送者发送给多个接收者（点对多点）。个人通信，如两个人之间的电话对话或传真信息，通常涉及点对点的传输。通常称为广播的点对多点电信传输，为商业无线电和电视节目播送提供了基础。第9页，此课件共37页哦 Telecommunications begin with messages that are converted into electronic signals.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 variety of ways to create and decode signals,and many different ways to transmit signals.第10页，此课件共37页哦电信以信息转换为电子信号为开端。然后，这些信号通过媒介发送到接收机，并在那里解码，恢复为接收信息的人能够理解的形式。有各种方法可以生成并解译信号，也有许多不同方法可以传输信号。第11页，此课件共37页哦 Devices such as the telegraph and telephone relay messages by creating modulated electrical impulses,or impulses that change in a systematic way.These impulses are then sent by wires,radio waves,or other media to a receiver that decodes the modulation.The telegraph,the earliest method of delivering telecommunications,works by converting the contacts(connections between two conductors that permit a flow of current)between a telegraph key and a metal conductor into electrical impulses.These impulses are sent along a wire to a receiver,which converts the impulses into short and long bursts of sound or into dots and dashes on a simple printing device.第12页，此课件共37页哦电报机与电话机等设备，通过生成调制电脉冲或以系统化方式变化的脉冲，来传递信息。接下来，这些脉冲通过导线、无线电波或其他媒介发送给接收机，并由其进行解调。电报机是最早的传递电信信息的方法，它通过将电报电键与金属导体之间的接触（使电流得以流动的两个导体之间的连接）转换成电脉冲而进行工作。这些脉冲沿着导线发送到接收机，而接收机则将这些脉冲转换成长与短的声音脉冲串，或者在简单的打印设备上打印出来的点与划。第13页，此课件共37页哦 Specific sequences of dots and dashes represents letters of the alphabet.In the early days of the telegraph,these sequences were decoded by telegraph operators.In this way,telegraph operators could transmit and receive letters that spelled words.Later versions of the telegraph could decipher letters and numbers automatically.Telegraphs have been largely replaced by other forms of telecommunications,such as fax machines and electronic mail(E-mail),but they are still used in some parts of the world to send messages.第14页，此课件共37页哦特定的点与划序列代表字母表中的字母。在早期的电报中，这些序列由电报机操作员进行解译。这样，电报机操作员就可以发送和接收可拼成词语的字母。后来的电报机能自动解译字母和数字。电报机在很大程度上已被其他的电信形式所取代，如传真机和电子邮件，但在世界有些地方，电报机仍然用来发送信息。第15页，此课件共37页哦 Telegraphs,telephones,radio,and television all work by modifying electronic signals,making the signals imitate,or reproduce,the original message.This form of transmission is known as analog transmission.Computers and other types of electronic equipment,however,transmit digital information.Digital technologies convert a message into electronic form first by measuring different qualities of the messages,such as the pitch and volume of a voice,many times.These measurements are then encoded into multiple series of binary numbers,or 1s and 0s.第16页，此课件共37页哦电报机、电话机、无线电和电视都是通过修改电子信号，使其模拟或再现原来的信息，来进行工作的。这种传输称为模拟传输。然而，计算机和其他类型的电子设备是传输数字信号的。数字技术将信息转换成电子形式。其方法首先是多次测量信息的不同特性，如语音的音高和音量。然后，这些测量值被编译成多个系列的二进制数或1与0。第17页，此课件共37页哦 Finally,digital technologies create and send electrical impulses that correspond to the series of 1s and 0s.Digital information can be transmitted faster and more clearly than analog signals,because the electrical impulses only need to correspond to two digits and not to the full range of qualities that compose the original message,such as the pitch and volume of a human voice.While digital transmissions can be sent over wires,cables or radio waves,they must be decoded by a digital receiver.New digital telephones and televisions are being developed to make telecommunications more efficient.第18页，此课件共37页哦最后，数字技术生成并发送与这些系列的1和0相对应的电脉冲。与模拟信号相比较，数字信息可以更快、更清晰地传输，因为电脉冲仅需与两个数字对应，而不是构成原信息的所有特性，如人的说话声的音高和音量。数字信息可以通过导线、电缆或无线电波传输，但必须由数字接收机进行解译。新型数字电话和电视正在开发中，以提高电信的效率。第19页，此课件共37页哦 Most personal computers communicate with each other and with larger networks,such as the Internet,by using the ordinary telephone network.Since the telephone network functions by converting sound into electronic signals,the computer must first convert its digital data into sound.Computers do this with a device called a modem,which is short for modulator/demodulator.A modem converts the stream of 1s and 0s from a computer into an analog signal that can then be transmitted over the telephone network,as a speakers voice would.The modem of the receiving computer demodulates the analog sound signal back into a digital form that the computer can understand.第20页，此课件共37页哦大多数个人计算机通过使用普通电话网，来进行彼此间的通信以及与因特网等大型网络的通信。因为电话网是通过将语音信号转换成电子信号来工作的，计算机必须首先将其数字数据转换成语音信号。计算机使用称为调制解调器的设备来完成这项工作。调制解调器是调制器/解调器的缩略。调制解调器将计算机输出的1和0数字流转换成模拟信号，而模拟信号可随后通过电话网传输，就像通话者的声音那样。接收端计算机的调制解调器将模拟语音信号解调还原为计算机能理解的数字形式。第21页，此课件共37页哦 Telecommunications systems deliver messages using a number of different transmission media,including copper wires,fiber-optic cables,communication satellites,and microwave radio.One way to categorize telecommunications media is to consider whether or not the media uses wires.Wire-based(or wireline)telecommunications provide the initial link between most telephones and the telephone network,and are a reliable means for transmitting messages.Telecommunications without wires,commonly referred to as wireless communications,using technologies such as cordless telephones,cellular radio telephones,walkie-talkies,citizens band(CB)radios,pagers,and satellites.Wireless communications offer increased mobility and flexibility.第22页，此课件共37页哦电信系统使用多种不同的传输媒介传送信息，包括铜线、光缆、通信卫星和微波无线电。划分电信媒介的一种方法，是看媒介是否使用导线。基于导线（或有线）的电信提供了大多数电话与电话网之间的最初链路，是一种可靠的信息传输方式。没有导线的电信，通常称为无线通信，使用无绳电话、蜂窝式无线电话、步话机、民用波段无线电台、寻呼机和卫星等技术。无线通信提高了机动性和灵活性。第23页，此课件共37页哦 Individual people,businesses,and governments use many different types of telecommunications systems.Some systems,like 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 signals through space,which 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.第24页，此课件共37页哦个人、企业和政府使用多种不同的电信系统。有些系统，如电话系统，使用由电缆、导线和交换台组成的网络，来进行点对点的通信。另外一些系统，如无线电台与电视台，通过空间播出信号，任何拥有接收设备的人都可以接收。有些系统利用数种媒介完成传输。例如，一个电话从打电话的人传送到接电话的人，其间可能要通过铜线、光缆和无线电波进行传输。随着电信技术的发展，所有的电信系统都在不断地演变。第25页，此课件共37页哦 Computer telecommunications,with the ability to send and receive audio,video,text,software,and multimedia,is one of the fastest growing segments of the telecommunications market.Computer telecommunications takes advantage existing telephone connections to transmit digital data.This type of transmission is frequently done over the Internet,a decentralized network of personal,business,government,and educational computers,and sources of information.Some computers connect directly to the digital portion of the telephone network using the Integrated Services Digital Network(ISDN),but this requires the installation of special devices and telephone line,called Digital Subscriber Line(DSL),is being developed to increase modem speed tremendously.第26页，此课件共37页哦计算机远程通信具有发送和接收音频信号、视频信号、文本、软件和多媒体的能力，是电信市场发展最快的部分之一。计算机远程通信利用现有的电话连接来传输数字数据。这种传输常常通过因特网进行，而因特网是一个由个人、企业、政府和教育机构所使用的计算机和信息源构成的分散型网络。有些计算机使用综合业务数字网（ISDN）直接连接到电话网的数字部分，但这需要安装专门设备和进行电话线调整。为了大幅度提高调制解调器的速度，目前正在开发一种供常规电话线使用的改进型调制解调器系统，称为数字用户线路（DSL）。第27页，此课件共37页哦 Electronic mail,or e-mail,is a key attraction of the Internet and a common form of computer telecommunications.E-mail is a text-based message delivery system that allows information such as typed messages and multimedia to be sent to individual computer users.Local e-mail messages(within a building or a company)typically reach addressees by traveling through wire-based internal networks.E-mail that must travel across town or across a country to reach the final destination usually travels through the telephone network.Other computer telecommunications technologies that businesses frequently use include automated banking terminals and devices for credit card transactions that bill charges directly to a customers bank account.第28页，此课件共37页哦电子邮件是因特网吸引人的一个关键点，也是计算机远程通信的一种常见形式。电子邮件是基于文本的信息传输系统，它能将键入的信息和多媒体信息等发送给个人计算机用户。（一幢建筑或一家公司内的）本地电子邮件通常经由基于导线的内部网传送给收件人。必须横穿城镇或国家才能到达最终目的地的电子邮件，通常通过电话网进行传输。企业经常使用的其他计算机远程通信技术包括自动银行终端及设备，用来处理将费用直接从顾客银行帐户上扣除的信用卡业务。第29页，此课件共37页哦 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.Innovations in fiber-optic technology will hopefully keep up with the growing use of personal computers for telecommunications.The next generation of cellular telephones,pagers,and televisions will also benefit from the speed and clarity of digital telecommunications.第30页，此课件共37页哦随着越来越复杂的计算机信息以快速提高的速度通过电话线发送，个人计算机拓展了电话系统的作用范围。这种对速度的需要促进了数字传输技术的发展。光纤技术的革新有望跟上个人计算机在远程通信方面不断增长的使用。下一代蜂窝电话、寻呼机和电视机也将受益于数字远程通信的速度和清晰度。第31页，此课件共37页哦 Telecommunications and information technologies are merging and converging.This means that many of the devices that we associate 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 about callers.第32页，此课件共37页哦电信和信息技术正在融合。这意味着，在我们只将其与一种功能联系起来的设备中，有不少可能演变为多用途设备。这种融合已经开始在各种领域发生。有些电话机和寻呼机不但能存储电话号码，而且还能存储呼叫者的姓名和个人信息。第33页，此课件共37页哦 Advanced phones with keyboards and small screens are now in development that can access the Internet and send and receive e-mail.Personal computers can now access information and video entertainment and are in effect becoming a combined television set and computer terminal.Television sets,which we currently associate with broadcast and cable-delivered video programming,are able to gain access to the Internet through add-on appliances.Future modifications and technology innovations may blur the distinctions between appliances even more.第34页，此课件共37页哦现在正在研制带有键盘和小屏幕的先进电话机，可用于访问因特网和接发电子邮件。个人计算机现在可以访问信息和视频娱乐节目，实际上正在成为电视机和计算机终端的组合体。我们当前将其与广播和电缆传输的视频节目联系在一起的电视机，可以通过附加的设备访问因特网。未来的改进和技术革新可能使设备之间的区别进一步模糊化。第35页，此课件共37页哦 Convergence telecommunications technologies will also trigger a change in the content available and the composition of the content providers.Both television and personal computers will be incorporating new multimedia,interactive,and digital features.For example,an entertainment program might have on-screen pointers to World Wide Web pages containing more information about the actors.In the near term,before the actualization of a fully digital telecommunications world,devices like modems will still be necessary to provide an essential link between the old analog world and the upcoming digital one.第36页，此课件共37页哦电信技术的融合也将在可获得的内容以及内容提供者的构成方面引起改变。电视机和个人计算机都将不断地吸纳新的多媒体、交互和数字化特征。例如，一个娱乐节目可能会有屏幕指针，链接到含有演员更多信息的万维网网页上。从近期来看，在全数字化电信时代到来之前，调制解调器等设备在为旧的模拟世界与即将到来的数字世界提供基本链接方面，仍然必不可少。第37页，此课件共37页哦