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COMMUNICATION CHANNELSCommunication channels are an essential element of every communication system. These channels actually carry the data from one computer to another. There are two categories of communication channels. One category connects sending and receiving devices by providing a physical connection such as a wire or cable. The other category is wireless.沟通渠道是一个至关重要的元素的每个通信系统。
这些渠道实际上把数据从一台计算机到另一个。
有两个类别的沟通渠道。
一个类别连接发送和接收设备通过提供一个物理连接导线或电缆等。
另一类是无线。
PHYSICAL CONNECTIONSPhysical connections use a solid medium to connect sending and receiving devices. These connections include telephone lines (twisted pair), coaxial cable,and fiber-optic cable.物理连接使用固体介质连接发送和接收设备。
这些连接包括电话线路(双绞线)、同轴电缆和光纤电缆。
Telephone lines you see strung on poles consist of twisted-pair cable,which is made up of hundreds of copper wires. A single twisted pair culminates in a wall jack into which you can plug your phone and computer. (See Figure 9-3.) Telephone lines have been the standard transmission medium for years for both voice and data. However, they are now being phased out by more technically advanced and reliable media.Coaxial cable, a high-frequency transmission cable, replaces the multiple wires of telephone lines with a single solid-copper core. (See Figure 9-4.) In terms of the number of telephone connections, a coaxial cable has over 80 times the transmission capacity of twisted pair.Coaxial cable is used to deliver television signals as well as to connect computers in a network..电话线路你看到两极串在由双绞线,是由数以百计的铜线。
计算机专业英语Unit-9Unit 9 Computer VirusText 1 Virus IntroductionExercises1. Multiple choices.(1)A virus is a ( A ).A. programB. computerC. bad manD. beast(2)A virus is a program that reproduces itsown code by ( ABC ).A. adding to the end of a fileB. inserting into the middle of a fileC. simply placing a pointerD. replacing another program(3)( AD )is a type of executable file .A. COM fileB. TXT fileC. JPG fileD. EXE file(4)Similar to viruses, you can also findmalicious code in ( ABC ).A. Trojan HorsesB. wormsC. logic bombsD. Microsoft Word Documents2. Fill in the blanks.(1)A virus is a program that reproduces itsown code by attaching itself to otherexecutable files in such a way that thevirus code is executed when the infectedexecutable file is executed .(2)To attach might mean physically addingto the end of a file, inserting into themiddle of a file, or simply placing apointer to a different location on the disksomewhere where the virus can find it. (3)Similar to viruses, you can also findmalicious code in Trojan Horses, worms,and logic bombs.3. Translate and analyze thefollowing sentences.(1)These self-replicating codes, when caused3by some event, may do a potentiallyharmful act to your computer.句子组成：when引导时间状语从句做插入语，当…的时候.翻译：当这些自复制代码被一些事件触发时，或许会做出一些对你的计算机有潜在危害的行为.(2)More recently, scripts written for Internetweb sites and/or included in E-mail canalso be executed and infected.句子组成：scripts written…省略的定语从句完整形式scripts which were writtened….翻译：现在，为网站编写的或者包括在E-mail 中的脚本也能够被执行和感染。
.教案首页（第11次课，2学时）授课题目Unit 9 Data Transimission Media教学目的通过讲授，使学生了解各种传输媒介的英文描述与要求教学重点传输媒介的专业术语教学难点课文的理解、翻译教学内容：单词、课文教学过程教学方法：讲授法课后作业P128-133，1-5教学后记Unit 9 Data Transimission Media一、传输媒介支持数据传输的传输媒介有：电话线、同轴电缆、微波信号、卫星系统和光纤。
电话线即为双绞线，它由四对线组成，其中每对由两条带绝缘层的导线以螺旋形式绞合在一起。
传输距离小，抗干扰能力弱、但价格便宜。
同轴电缆：由内外两个导体构成，内导体是一根铜质导线，外导体是铜箔构成，起屏蔽干扰作用。
传输距离适中、抗干扰能力强。
光纤：光缆纤缆作为信号传输介质，把电信号转换成光信号，进行传输。
传输距离远、抗干扰能力强、传输信号量大且信号不失真，但价格贵。
二、New Words1．amplifier n.放大器，扩音机2. antenna n.触角，触须；天线3. boost vt.提高；推动；宣扬n.增涨；推动，激励Boost an electric current增强电流Give sb’s confidence a boost增强某人的信心4. channel n.频道；信道；沟渠；海峡，航道Your favourite channel你最喜欢的频道5. circuit n.电路，线路；环行，环行道The circuit of the city is three miles.环城线路有三英里。
6. coaxial同轴的; 共轴; 共轴的7. compensate v.补偿，弥补，抵消She was compensated by the insurance company for her injuries.她受伤后获得保险公司的赔偿。
8. curvature弧度，曲率，弯曲The curvature of the earth ‘s surface.地球表面的曲度。
