计算机专业英语部分文章翻译.docx

1、计算机专业英语部分文章翻译 Communication 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

2、 such as a wire or cable. The other category is wireless. 通信管道对于每一个通信系统来说是一个至关重要的元素。这些管道实际上把数据从一台计算机传输到另一台。有两个类别的通信管道。一类是有线，另一类是无线。PHYSICAL CONNECTIONS Physical connections use a solid medium to connect sending and receiving devices. These connections include telephone lines (twisted pair), coaxial

3、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 Figur

4、e 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 singl

5、e 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. 你所看到的电话线，是由上百根铜线缠绕而成的双绞线。双绞线的一个端口是固定电话

6、,当然也可以插在手机和电脑上。电话线作为一个标准传输媒介，多年一来一直在负责语音和数据的传输。然而,他们现在已经被更先进、可靠的媒体所淘汰了。同轴电缆、高频传输电缆,取代了多个连接的电话线。在传输能力方面,一个同轴电缆是双绞线传输容量的80倍。同轴电缆先主要用于提供电视信号以及连接网络的电脑. . Fiber-optic cable transmits data as pulses of light through tiny tubes of glass. (See Figure 9-5.) In terms of the number of telephone connections,fib

7、er-optic cable has over 26,000 times the transmission capacity of twisted-pair cable. Compared to coaxial cable, they are lighter and more reliable at transmitting data. They transmit information using beams of light at light speeds instead of pulses of electricity, making them far faster than coppe

8、r cable. Fiber-optic cable is rapidly replacing twisted-pair cable telephone lines.光纤电缆传输数据是由光脉冲在细小的玻璃导管内进行的。(参见图9 - 5)。在传输能力上，光纤电缆的传输速度已经超过双绞线26000倍。与同轴电缆相比,光纤更轻，传输更快。光纤使用光束传输信息，而不是的电脉冲,这使他们传输速度远远快于铜电缆。光纤电缆正在迅速取代电缆电话线路。 244WIRELESS CONNECTIONS Wireless connections do not use a solid substance to co

9、nnect sending and receiving devices.Rather, they use the air itself. Primary technologies used for wireless connections are infrared, broadcast radio, microwave, and satellite. 无线连接不使用固体物质连接发送和接收数据。相反,他们使用空气本身传播。目前此项技术主要用于红外连接、广播无线电、微波和卫星。 Infrared uses infrared light waves to communicate over short

10、 distances.It is sometimes referred to as line-of-sight communication because the light waves can only travel in a straight line. This requires that sending and receiving devices must be in clear view of one another without any obstructions blocking that view.One of the most common applications is t

11、o transfer data and information from a portable device such as a notebook computer or PDA to a desktop computer. 红外技术使用红外光波在短距离通信。它有时被称为视距通信，因为光只能沿直线传播。这就要求发送和接收设备必须没有任何障碍物阻止。最常见的应用是用来传送数据和信息从一个便携式设备，如笔记本电脑或掌上电脑桌面计算机上传输数据。 Broadcast radio uses radio signals to communicate with wireless devices.For e

12、xample, cellular telephones and many Web-enabled devices use broadcast radio to place telephone calls and/or to connect to the Internet. Some end users connect their notebook or handheld computers to a cellular telephone to access the Web from remote locations. Most of these Web-enabled devices foll

13、ow a standard known as Wi-FI (wireless fidelity). This wireless standard is widely used to connect computers to each other and to the Internet. 广播电台使用无线电信号与无线设备。例如,移动电话和许多网络设备使用广播电台将电话和/或连接到互联网。一些终端用户连接他们的笔记本通过无线信号连接上网。大多数的这些网络设备遵循一个标准，称为wi - fi。这个无线标准被广泛用于局域网和因特网。 Microwave communication uses high-

14、frequency radio waves. Like infrared, microwave communication provides line-of-sight communication because microwaves travel in a straight line. Because the waves cannot bend with the curvature of the earth, they can be transmitted only over relatively short distances. Thus, microwave is a good medi

15、um for sending data between buildings in a city or on a large college campus. For longer distances, the waves must be relayed by means of microwave stations with microwave dishes or antennas. (See Figure 9-6.) These stations can be installed on towers. high buildings. and mountaintoos. 微波通信使用高频无线电波。

16、如红外、微波通信只能提供短距通信因为微波以直线的方式行进。因 此,微波是非常适合用来在大城市或者校园内作为数据传输的媒介。微波发射台可以安装在塔或者高的建筑之上。 Bluetooth is a short-range wireless communication standard that uses microwaves to transmit data over short distances of up to approximately 33 feet. Unlike traditional microwaves,Bluetooth does not require line-of-sig

17、ht communication. Rather, it uses radio waves that can pass through nearby walls and other nonmetal barriers. It is anticipated that within the next few years, this technology will be widely used to connect a variety of different communication devices. 蓝牙是一种短距离的无线通信标准,通信距离大约33英尺。与传统的微波相比,蓝牙不需要视距通信。相

18、反,它使用无线电波可以穿透附近的墙壁和其他非金属壁垒。在未来几年中,这种技术将被广泛用于连接各种不同的通信设备。 Satellite communication uses satellites orbiting about 22,000 miles above the earth as microwave relay stations. (See Figure 9-7.) Many of these are offered by Intelsat, the International Telecommunications Satellite Consortium, which is owned

19、 by 114 governments and forms a worldwide communication system. Satellites rotate at a precise point and speed above the earth. They can amplify and relay microwave signals from one transmitter on the ground to another. Satellites can be used to send and receive large volumes of data. Uplink is a te

20、rm relating to sending data to a satellite.Downlink refers to receiving data from a satellite. The major drawback to. 卫星通信使用在离地约22000英里的轨道卫星作为微波中继站。许多这些提供的国际通信卫星、国际通信卫星的财团旗下有和114政府相联合，形成一个全球通信系统。卫星旋转在定位精确，速度高于地球。他们可以通过地面发射机放大微波信号转发到另一个地面站。卫星可以用来发送和接收大量的数据。上行链路是一个术语，涉及将数据发送到卫星。下行是指从卫星接收数据。One of the

21、most interesting applications of satellite communications is for global positioning. A network of 24 satellites owned and managed by the Defense Department continuously sends location information to earth. Global positioning system (GPS) devices use that information touniquely determine the geograph

22、ical location of the device. Available in some automobiles to provide navigational support, these systems are often mounted into the dash with a monitor to display maps and speakers to provide spoken directions. (See Figure 9-8.) 其中最有趣的应用卫星通信是为全球定位。一个拥有24个卫星的网络，国防部管理。全球定位系统(GPS)设备的独特功能决定了它可以为汽车提供导航支

23、持,这些系统通常安装到汽车上，通过仪表和声音为车主提供导航。 245A great deal of computer communication takes place over telephone lines. However, because the telephone was originally designed for voice transmission, telephones typically send and receive analog signals, which are continuous electronic waves. Computers, in contras

24、t, send and receive digital signals. (See Figure 9-10.) These represent the presence or absence of an electronic pulse-the on/off binary signals we mentioned in Chapter 6. To convert the digital signals to analog signals and vice versa, you need a modem.大量的计算机通信通过电话线传播。然而,由于电话最初是设计用来传输信息，所以只发送和接收模拟信

25、号。相反,不发送和接收数字信号。(参见 图9)。所以想用电话线来上网，你需要一个调制解调器MODEMSThe word modem is short for modulator-demodulator. Modulation is the name of the process of converting from digital to analog. Demodulation is the process of converting from analog to digital. The modem enables digital microcomputers to communicate

26、across analog telephone lines. This communication includes both voice and data communications.调制解调器简称猫。调制指数字信号转换转换为模拟信号。解调指从模拟信号转化为数字信号，现代通信使数字计算机能模拟电话线路。从而实现语音交流和数据通信。 The speed with which modems transmit data varies. This speed,called transfer rate, is typically measured in bits per second (bps).(

27、See Figure 9-11.) The higher the speed, the faster you can send and receive information. For example, transferring an image like Figure 9-10 might take 75 seconds with a 33.6 kbps modem and only 45 seconds with a 56 kbps modem.调制解调器的传输数据的速度称为传输速率,以比特/秒(bps)为单位。速度越高,你可以越快地发送和接收信息。 There are four basi

28、c types of modems:external, internal, PC Card, and wireless. 调制解调器分为四种：外置、集成、芯片、和无线The external modem stands apart from the computer and typically is connected by a cable to the computers serial port. Another cable connects the modem to the telephone wall jack.外部调制解调器除了电脑,通常由电缆连接到计算机的串行端口。另一个电缆连接调制解

29、调器固定电话 The internal modem consists of a plug-in circuit board inside the system unit. A telephone cable connects the modem to the telephone wall jack.、 内部调制解调器包含插件电路板系统内的单位。电话电缆连接墙上电话端口。The PC Card modem is a credit card-size expansion board that is inserted into portable computers. A telephone cabl

30、e connects the modem to the telephone wall jack. 卡片调制解调器是一种信用卡大小的卡片,插入到手提电脑。电话端连接到固定电话端口247A wireless modem may be internal, external,a PC Card.一个无线调制解调器可能是内置的、外置的的、或者一个电脑芯片。Unlike the other modems, it does not use cables. Instead,wireless modems send and receive through the air.与其他调制解调器不同,它不使用电缆。相反

31、,无线调制解调器通过无线电波发送和接收。Standard telephone lines and conventional modems provide what is called a dial-up service. 标准电话线路和传统的调制解调器提供一般的的拨号服务。Although still the most popular type of connection service,dial-up service is quite slow, and many users find it inadequate to meet their communication needs.虽然仍然是

32、最受欢迎的连接服务,但是拨号服务相当慢,很多用户发现它不足以满足需求。For years, large corporations have been leasing special high-speed lines from telephone companies. 多年以来,大型公司已经从电信公司租赁使用特殊的高速线路。These lines-known as T1, T2, T3, and T4 lines-support all digital communications, do not require conventional modems, and provide very high capacity. 这些线已知为T1、T2、T3、T4，这些线路支持所有数字通信,不需要传统的调制解调器,并提供非常高的传输能力Unfortunately, this type of connection is very expensive.不幸的是,这类线路的连接费用非常昂贵For example,T1 lines provide a speed of 1.5 mbps (over 26 times as fast as a conventional modem) and cost several thousand dollars.