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There are several factors that affect data transmission. They include speed or bandwidth, serial or parallel transmission, direction of data flow, modes of transmission data, and protocols.
Bandwidth The different communications channels have different data transmission speeds. This bit-per-second transmission capability of a channel is called its bandwidth. Bandwidth may be of three types: voiceband, medium band and broadband. Voiceband is the bandwidth of a standard telephone line and used often for microcomputer transmission, the bps is 300~9600. Medium band is the bandwidth of special liased lines used mainly with minicomputers and mainframe computers, the bps is 56,000~264 million. Broadband is the bandwidth that includes microwave, satellite, coaxial cable, and fiber-optic channels. It is used for very high-speed computers whose processors communicate directly with each other. It is in the range of 56,000~30 billion bps.
Serial or Parallel Transmission Data travels in two ways: serially and in parallel. In serial data transmission, bits flow in a serial or continuous stream, like cars crossing a one-lane bridge. Each bit travels on its own communications line. [1] Serial transmission is the way most data is sent over telephones lines. Thus, the plug-in board making up the serial connector in a microcomputer's modem is usually called a serial port. More technical names for the serial port are RS-232C connector and asynchronous communications port. With parallel data transmission, bits flow through separate lines simultaneously. In other words, they resemble cars moving together at the same speed on a multilane freeway. Parallel transmission is typically limited to communications over short distances and is not used over telephone lines. It is, however, a standard methods of sending data from a computer's CPU to a printer.
Direction of Data Transmission There are three directions or modes of data flow in a data communications system: simplex communication, half-duplex communication, and full-duplex communication. Simplex communication resembles the movement of cars on a one-way street. Data travels in one direction only. It is not frequently used in data communication systems today. One instance in which it is used may be in point-of sale (POS) terminals in which data is being entered only. In half-duplex communication, data flows in both directions, but not simultaneously. That is, data flows in only one direction at any one time. This resembles traffic on a one-lane bridge. Half-duplex is very common and is frequently used for linking microcomputers by telephone lines to other microcomputers, minicomputers, and mainframes. Thus, when you dial into an electronic bulletin board through your microcomputer, you may well be using half-duplex communication. In full-duplex communication, data is transmitted back and forth at the same time, like traffic on a two-way street. It is clearly the fastest and most efficient form of two-way communication. However, it requires special equipment and is used primarily for mainframe communications. An example is the weekly sales figures that a supermarket or regional office sends to its corporate headquarters in another place.
Modes of Transmitting Data Data may be sent by asynchronous or synchronous transmission. In asynchronous transmission, the method frequently used with microcomputers, data is sent and received one byte a time. Asynchronous transmission is often used for terminals with slow speeds. Its advantage is that the data can be transmitted whenever convenient for the sender. Its disadvantage is a relatively slow rate of data transfer. Synchronous transmission is used to transfer great quantities of information by sending several bytes or a block at a time. For the data transmission to occur, the sending and receiving of the blocks of bytes must occur at carefully timed intervals. Thus, the system requires a synchronized clock. Its advantage is that data can be sent very quickly. Its disadvantage is the cost of the required equipment.
Protocols For data transmission to be successful, sender and receiver must follows a set of communication rules for the exchange of information. These rules for exchanging data between computers are known as the line protocol. A communication software package like Crosstalk helps define the protocol, such as speeds and modes, for connecting with another microcomputer. TCP/IP (Transmission Control Protocol and Internet Protocol) are the two standard protocols for communications on the Internet.
TCP/IP is the "language" of the Internet. It is a networking technology developed by the United States Government Defense Advanced Research Project Agency (DARPA) in the 1970s. It is most commonly employed to provide access to the Internet but can be and is used by many people to create a LAN that may or may not connect to the Internet. In many aspects TCP/IP is a client/server-type LAN, but many manufacturers of TCP/IP software have applications that allow the "clients" to serve files or even applications. TCP/IP is truly an open systems protocol. This means that no one manufacturer creates the product—any computer running TCP/IP software can connect to anyone else who has TCP/IP software (provided the user has an account and security permissions), regardless of who made the particular version of software.
When different types of microcomputers are connected in a network, the protocols can become very complex. Obviously, for the connections to work, these network protocols must adhere to certain standards. The first commercially available set of standards was IBM's Systems Network Architecture (SNA). This works for IBM's own equipment, but other machines won't necessarily communicate with them. The International Standards Organization has defined a set of communications protocols called the Open Systems Interconnection (OSI). The purpose of the OSI model is to identify functions provided by any network. [2] It separates each network's functions into seven "layers" of protocols, or communication rules. When two network systems communicate, their corresponding layers may exchange data. [3] This assumes that the microcomputers and other equipment on each network have implemented the same functions and interfaces.
Words
| adhere | v. | 黏着于（坚持，追随）…… |
| assume | v. | 假定，设想，采取，呈现 |
| asynchronous | adj. | 异步的 |
| broadband | n. | 宽频带，宽波段 |
| bulletin | n. | 公报，通报，告示 |
| duplex | adj. | 双工的，双向的 |
| implement | v. | 实现，完成 |
| interface | n. | 界面 |
| parallel | adj. | 平行的，并联的 |
| protocol | n. | 协议 |
| serial | adj. | 连续的，串联的 |
| simplex | adj. | 单工的，单向的 |
| voiceband | n. | 话音频带 |
Phrases
| dial into | 拨入 |
| open system protocol | 开放系统协议 |
Abbreviations
| OSI (Open Systems Interconnection) | 开放系统互连 |
| POS (Point-Of-Sale) | 零售点 |
| SNA (Systems Network Architecture) | 系统网络结构 |
| TCP/IP (Transmission Control Protocol and Internet Protocol) | 传输控制协议和因特网协议 |
Notes
［1］ 例句：Serial transmission is the way most data is sent over telephones lines.
分析：most data is sent over telephones lines是定语从句，修饰the way。
译文：串行传输是绝大多数数据通过电话线传输的方式。
［2］ 例句：It separates each network's functions into seven "layers" of protocols, or communication rules.
分析：短语separate…into…意思是“把……分成……”。
译文：它把每个网络的功能分成七层协议，即七层通信规则。
［3］ 例句：This assumes that the microcomputers and other equipment on each network have implemented the same functions and interfaces.
分析：句中that引导的是宾语从句，作assumes的宾语。
译文：这种情况假设每一个网络中的微机和其他设备实现了同样的功能，具有同样的接口。
Exercises
Ⅰ. Put "true" or "false" in the brackets for the following statements according to the passage.
1. ( ) Protocols is the main factor that affects data communication.
2. ( ) Broadband is suitable for all kinds of communication channels and is mainly used for high-speed computers.
3. ( ) Serial and parallel transmission are the two ways of data traveling, they can't be replaced with each other.
4. ( ) In asynchronous transmission, the method frequently used with microcomputers, data is sent and received several bytes a time.
5. ( ) Simplex communication is very common and is frequently used for linking microcomputers by telephone lines to other microcomputers, minicomputers, and mainframes.
6. ( ) TCP/IP is the "language" of the Internet, which can only be used on internet.
7. ( ) Protocols are a set of communication rules for sender and receiver to exchange data.
8. ( ) An open system protocol means that no special product will be needed, and only those that obey the protocol will be admitted and can share resources.
9. ( ) The purpose of the OSI model is to identify functions provided by any network.
10. ( ) OSI model assumes that the microcomputers and other equipment on each network have implemented the same functions and interfaces.
Ⅱ. Fill in the blanks according to the passage.
1. There are several factors that affect data transmission. They include speed orserial ortransmission,of data flow, modes of transmission data, and.
2. In serial data transmission, bits flow in a serial orstream.
3. With parallel data transmission, bits flow throughlines simultaneously.
4. is very common and is frequently used for linking microcomputers by telephone lines to other microcomputers, minicomputers, and mainframes.
5. Incommunication, data is transmitted back and forth at the same time.
6. Asynchronous transmission is often used for terminals with.
7. Synchronous transmission requires aclock.
8. TCP/IP (Transmission Control Protocol and Internet Protocol) are the two standard protocols for communications on the.
9. The OSI model separates each network's functions into seven "layers" of, or communication rules.
10. TCP/IP is truly an open systems protocol. This means that no one manufacturer creates the product—any computer running TCP/IP software canto anyone else who hassoftware regardless of who made the particular version of software.
Ⅲ. Translate the following words and expressions into Chinese.
1. protocol
2. modes of transmission data
3. transmission control protocol
4. asynchronous
5. serial transmission
6. full-duplex communication
7. point-of sale terminal
8. broadband
9. electronic bulletin board
10. channel
This document discusses checking to see if your computer has TCP/IP installed. Important: If your company has an network, or computer, administrator, then please consult them before making changes to a computer's network settings! The installation of TCP/IP can vary from one version of Windows to another, so make sure you match the instruction set below to your copy of Windows.
Windows XP automatically detects whether your machine is using TCP/IP, and disables it if it is not! So first you must determine whether the machine has TCP/IP installed on a modem or on a network connection or, of course, not at all. In order to do this, please follow these simple instructions:
1) Select the Start button, then the Settings menu, and then the Control Panel from the Settings menu.
2) Double click on Network Connections.
3) This should show a window of all network related connections.
i. If there are no icons under Dial up or LAN, then you don't have any network or dial up connections, and therefore, no TCP/IP. For now, you can close all windows to return to your desktop.
ii. If you don't have any LAN type connections, you can close all windows to return to your desktop. Otherwise, continue with step 4.
4) Right click on the any of the network (those that say LAN) icons and choose Properties.
5) On the General tab, look through the list and see if you can see Internet Protocol TCP/IP. You will need to repeat steps 4 and 5 for all LAN connections in the window.
6) If it is there, you have TCP/IP installed. If not, you don't have TCP/IP.
A) You don't have any network connections, or you have a modem, but need to ensure TCP/IP is enabled: You can install the Microsoft Loopback Adapter to take care of TCP/IP. Follow these easy instructions to install:
1) Select the Start button, then the Settings menu, and then the Control Panel from the Settings menu.
2) Double click on Add Hardware.
3) Click Next on the Add Hardware wizard.
4) Click Yes for Have you got the hardware connected, and then click Next.
5) Select Add new Hardware device from the list, and then Next.
6) Select Install the Hardware device that I manually select from a list (Advanced), and then click Next.
7) Click Network Adapters, and then click Next.
8) In the Manufacturers box, click Microsoft.
9) In the Network Adapters box, click Microsoft Loopback Adapter, and then click Next.
10) Click Next to start the installation.
B) You have a network card installed, but no TCP/IP: You may be using a different protocol on your network card, so TCP/IP may not be installed. Follow these steps to install:
1) Select the Start button, then the Settings menu, and then the Control Panel from the Settings menu.
2) Double click Network and Dial Up Connections.
3) Right click on the LAN connection, and choose Properties.
4) On the general tab, ensure that TCP/IP is not already in the list, and then click Install.
5) Select Protocol form the list, and click Add.
6) Wait a few seconds, and then select Internet Protocol TCP/IP, and click OK.
7) Wait a few seconds, and then check that TCP/IP shows up in the list on the General tab of the Network Connection Properties, and then close all windows to return to the desktop.
Words
| adapter | n. | 适配器，改编者 |
| automatically | adv. | 自动地，机械地 |
| check | v. | 检查，核对，寄存，托运 |
| consult | v. | 商量，商议，请教；参考，考虑 |
| desktop | n. | ［计］桌面；桌上型电脑 |
| disable | v. | 使残废，使失去能力 |
| ensure | v. | 保证，担保，使安全，确保 |
| icon | n. | 图标，肖像 |
| manually | adv. | 用手地；手工地 |
| manufacturer | n. | 制造业者，厂商 |
| property | n. | 财产，所有物，属性，特性 |
| tab | n. | 制表，标号，TAB键，标签，制表符 |
| vary | v. | 改变，变更，使多样化，变化，不同 |
Phrases
Control Panel ［计］控制面板
影响数据传送的几个因素，包括速度或带宽、串行或并行传送、数据流的方向、数据传送的方式及协议。
带宽 不同的通信信道有不同的数据传送速度。信道每秒钟能传送二进制位的能力被称为带宽。带宽有三种类型：语音频带、中速带宽和宽带。语音频带是标准电话线的带宽，通常被用于微型机的传送，其每秒钟传送的二进制位数是300到9600。中速带宽主要是由小型机和大型机使用的特殊连接线的带宽，其每秒钟传送的位数是56000到26.4亿。宽带包括微波、卫星、同轴电缆和光缆的信道的带宽。它主要用在处理器之间直接进行通信的高速计算机中，其每秒钟传送的位数为56000到300亿位。
串行或并行传输 数据以串行和并行两种方式传送。在串行数据传输中，数据位的流动是一串或连续的流量，就像汽车通过只有一个车道的桥。每一位在自己的通信线路上流动。串行传输是绝大多数数据通过电话线传输的方式。因此，构成微机调制解调器的串行连接器的插入板通常被称为串行口。串行口的技术名称是RS-232C连接器和异步通信端口。采用并行数据传输时，数据位是通过分离的线路同时流动的。换句话说，它们类似于汽车一起以同样的速度通过多道快车道。并行传送主要局限于短距离的传送，并不通过电话线。它是从计算机的CPU到打印机传送数据的标准方式。
数据传输的方向 在数据通信系统中数据流的方向（或方式）有三种：单工通信、半双工通信和全双工通信。单工通信类似于汽车在单向的街上行驶，数据仅以一个方向传送。它并不经常用于现在的数据通信系统中。使用单工通信的一个例子是只输入数据的零售点终端。在半双工通信中，数据以两个方向流动，但不是同时。也就是说，数据在任何时候都只以一个方向流动，这类似于只有一个车道的桥上的交通。半双工通信很普遍，经常应用于通过电话线连接的微型机之间、微型机和小型机及大型机之间的通信中。因此，当通过微机拨入到电子公告牌，也许使用的就是半双工通信。在全双工通信中，数据同时来回地传送，类似于双向街道上的交通。很显然全双工通信是双向通信中最快最有效的形式。但是，全双工通信需要特殊的设备并且主要用于大型机的通信。其应用的一个典型例子是超市或区域办公室每周将其销售的数据发送给在另一个地方的公司总部。
数据传送方式 数据能以异步或同步方式传送。在异步传送方式下，一次只能发送和接收一个字节，是微型机经常使用的方法。异步传送也常用于速度较慢的终端设备。其优点是在适当的时候发送方就可以传送数据。缺点是数据传送速率相对较慢。同步传送一次发送几个字节或数据块，用于大量信息的传送。为了实现数据传送，发送和接收的字节块必须以精确的时间间隔出现。因此，系统需要一个同步时钟。其优点是可以很快地传送数据，缺点是需要一定的设备费用。
协议 为了成功地传送数据，发送方和接收方必须遵循用于信息交换的一套通信规则。这些用于计算机之间交换数据的规则被称为是线路协议。为了和其他微机连接，像Crosstalk这样的通信软件包就帮助定义协议，诸如速度和方式。TCP/IP（传输控制协议和因特网协议）是Internet上用于通信的两个标准协议。
TCP/IP是Internet的“语言”，它是由美国政府防御高级研究项目机构在20世纪70年代开发的网络技术。它最常用于提供访问Internet，但也被许多人用于建立与Internet相联或不联的局域网。在许多方面，TCP/IP是客户服务器类型的局域网，但许多TCP/IP软件的生产商具有允许“客户机”提供文件甚至应用的应用软件。TCP/IP是一个真正的开放系统协议。这就意味着没有一个生产商生产这个产品——任何运行TCP/IP软件的计算机都可以和另一个具有TCP/IP软件的任一机器相联（假设该用户具有账号和安全许可），而不管是谁制定的这个软件版本。
当不同类型的微机在网络中相联时，协议将变得非常复杂。显然，为了实现通信，这些网络协议必须坚持一定的标准。第一套商业可用标准是IBM公司的系统网络结构，该标准只用于IBM自己的设备，不过，其他的机器不需要与它们交流。国际标准化组织已经制定了一套被称为开放系统互连的通信协议。开放系统互联模式的目的是判断由任一网络提供的功能。它把每个网络的功能分成七层协议，即七层通信规则。当两个网络系统通信时，它们的对应层可以交换数据。这种情况假设每一个网络中的微机和其他设备实现了同样的功能具有同样的接口。
本文讨论检查您的电脑是否已安装TCP/IP。重要提示：如果您的公司有网络或计算机的管理员，在改变计算机的网络设置之前请先咨询他们！根据Windows版本不同安装TCP/IP协议应也不同，因此先确认您的Windows版本是否与下述指令集匹配。
Windows XP会自动检测您的计算机是否正在使用TCP/IP，如果不是则停用它！因此，首先必须确定调制解调器或网络连接是否安装了TCP/IP。或者，什么都没有。为了做到这一点，请按照下面的简单说明操作。
1）选择开始按钮，再选择设置菜单，然后从设置菜单选择控制面板。
2）双击网络连接。
3）这样会显示一个所有与网络相关的连接的窗口。
i．如果没有拨号连接或局域网图标，说明您的电脑没有任何网络或拨号连接，因此，没有TCP/IP协议。这时应先关闭所有窗口返回到桌面。
ii．如果没有任何局域网连接类型，可以关闭所有窗口返回到桌面。否则，请继续步骤4）。
4）右击网络（即局域网）图标，并选择属性。
5）在常规选项卡中，查看列表，看看是否可以看到互联网协议TCP/IP。您需要对窗口中的所有LAN连接重复步骤4）和5）。
6）如果列表中有，表明已经安装了TCP/IP。如果没有，则说明没有安装TCP/IP。
A）您没有任何网络连接，或您有调制解调器，但需要确保TCP/IP协议已启用，这时可以安装Microsoft环回适配器以处理TCP/IP协议。按照以下的简单说明安装：
1）选择开始按钮，再选择设置菜单，然后从设置菜单选择控制面板。
2）双击添加硬件图标。
3）单击添加硬件向导中的下一步按钮。
4）在我已经连接了此硬件项单击“是”按钮，然后单击下一步。
5）从列表里选择添加新的硬件设备，然后单击下一步。
6）选择安装我手动从列表选择的硬件（高级），然后单击下一步。
7）单击网络适配器，然后单击下一步。
8）在制造商框中单击Microsoft。
9）在网络适配器框中单击Microsoft环回适配器，然后单击下一步。
10）单击下一步开始安装。
B）您已经安装了一个网络卡，但没有TCP/IP协议：您可能在网卡上使用了不同协议，所以可能尚未安装TCP/IP协议，这时按照以下步骤安装：
1）选择开始按钮，再选择设置菜单，然后从设置菜单选择控制面板。
2）双击网络和拨号连接。
3）右击局域网连接，并选择属性。
4）在常规选项卡上确认TCP/IP不在清单中，然后单击安装。
5）从列表中选择协议，并单击添加。
6）等待几秒钟，选择Internet协议TCP/IP，然后单击确定。
7）等待几秒钟，确保TCP/IP出现在网络连接属性的常规选项卡列表中，然后关闭所有窗口回到桌面。