计算机专业英语第九章部分翻译

COMMUNICATION CHANNELS

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 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 CONNECTIONS

Physical 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。一个双绞线的顶端是一墙杰克,你可以插你的手机和电脑。电话线被标准的传输介质多年的语音和数据。然而,他们现在被淘汰的技术更先进、可靠的媒体。同轴电缆、高频传输电缆,取代了多个连接的电话线和一个固体铜核心。在数量方面的电话连接,一个同轴电缆有超过80倍的双绞线传输容量。同轴电缆是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,fiber-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 copper cable. Fiber-optic cable is rapidly replacing twisted-pair cable telephone lines.

光纤电缆传输数据的光脉冲,通过微小的玻璃管。在数量方面的电话连接,光纤电缆已经超过26000倍的双绞线传输容量。同轴电缆相比,它们更轻和更可靠的传输数据。他们使用光束传输信息以光的速度而不是的电脉冲,使他们远远快于铜电缆。光纤电缆正在迅速取代双绞线电缆电话线路。

WIRELESS CONNECTIONS

Wireless connections do not use a solid substance to connect 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设备。相反,他们使用空气本身。主要技术用于无线连接红外、广播无线电、微波和卫星。

Infrared uses infrared light waves to communicate over short 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 to transfer data and information from a portable device such as a notebook computer or PDA to a desktop computer.

红外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波只能以直线的方式行进。这就要求发送和接收设备必须在清楚彼此的观点没有任何障碍物阻止这一观点。一个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。

Broadcast radio uses radio signals to communicate with wireless devices.For example, 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 follow 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或者掌上电脑到移动电话访问网络从远程位置。大多数的这些网络设备遵循一个标准的称为wi - fi(无线保真度)。这个无线标准被广泛用于连接电脑到对方和因特网。 Microwave communication uses high-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 medium 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 mountaintops.

微波通信使用高频无线电波。如红外、微波通信提供视距通信因为微波以直线的方式行进。因为海浪不能弯曲曲率的地球,他们可以传播只在相对较短的距离。因此,微波是一个很好的媒介建筑物之间发送数据在一个城市或一个大的大学校园。时间的距离,海浪必须转发通过微波站与微波碗或天线。这些站可以安装在大厦,高层建筑,山顶。

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-sight 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,使用微波传输数据在短的距离大约33英尺。与传统的微波,蓝牙不需要视距通信。相反,它使用无线电波可以通过附近的墙壁和其他非金属壁垒。预计在未来几年中,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 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 term relating to sending data to a satellite.Downlink refers to receiving data from a satellite. The major drawback to. 卫星通信使用卫星轨道在约22000英里的地球作为微波中继站。许多这些提供的国际通信卫星、国际通信卫星财团旗下114政府和形成一个全球通信系统。卫星旋转在一个精确的点和速度高于地球。他们可以放大和继电器微波信号从一个发射机在地上,另一个。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。的主要缺陷。

One of the 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 to uniquely determine the geographical 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。一个网络24卫星拥有和管理由国防部连续发送位置信息到地球。全球定位系统(GPS)设备使用这些信息来唯一地确定地理位置的装置。可以在一些汽车提供导航支持,这些系统通常安装到仪表板与监视显示地图和扬声器提供口头的方向。

CONNECTION DEVICES

A 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 contrast, 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.

大量的计算机通信发生于电话线然而,因为电话是最初设计用于语音传输、电话通常发送和接收模拟信号连续电子波。电脑,相反,发送和接收数字信号。这些代表的存在或缺少电子脉冲开/关二进制信号我们提到在第六章。转换为数字信号,模拟信号,反之亦然,你需要一个调制解调器。 MODEMS

The 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 across analog telephone lines. This communication includes both voice and data communications.

调制解调器是一词简称调制解调器。调制是进程的名称从数字模拟转换。解调是一个过程,从模拟到数字的转换。现代通信使数字微机在模拟电话线路。这种交流包括语音和数据通信。

The speed with which modems transmit data varies. This speed,called transfer rate, is typically measured in bits per second (bps).(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.

调制解调器的速度传输数据变化。这速度,称为传输速率,是典型的以比特/秒(bps)。速度越高,你越快可以发送和接收信息。例如,将一个图像与图9 - 10或许需要75秒33.6 kbps调制解调器和只有45秒一个56 kbps调制解调器。

There are four basic types of modems:external, internal, PC Card, and wireless. (See Figure 9-12.)

有四种基本类型的调制解调器:外部、内部、PC卡和无线。

? The external modem stands apart from the computer and typically is connected

by a cable to the computer's serial port. Another cable connects the modem to the telephone wall jack. 外部调制解调器站除了电脑,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调器墙上电话插孔

? 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。电话电缆连接调制解调器墙上电话插孔

? The PC Card modem is a credit card-size expansion board that is inserted into

portable computers. A telephone cable connects the modem to the telephone wall jack. PC卡调制解调器是一种信用卡片尺寸扩展板,插入到手提电脑。电话电缆连接调制解调器墙上电话插孔

? A wireless modem may be internal, external,a PC Card.Unlike the other

modems, it does not use cables. Instead,wireless modems send and receive through the air. 一个无线调制解调器可能是内部的、外部的、一个PC卡片。与其他调制解调器,它不使用电缆。相反,无线调制解调器发送和接收通过空气

Standard telephone lines and conventional modems provide what is called a dial-up service. 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. 标准电话线路和传统的调制解调器提供所谓的拨号服务。虽然仍然是最受欢迎

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