[计算机专业英语第九章部分翻译.docVIP

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 transmitt