Teaching Plan Lecturer Ren Jing Course English for Telecommunications Lesson Number 11(Unit 11)  Time  Grade  Teaching Mode Lecturing  Content Circuit Switching and Packet Switching Class Hours 2 Periods  Teaching Objectives 1.to know the development of switching techniques 2.to understand the main ideas of the text 3.to master the useful sentence structures, words and expressions used in the relevant exercises  Focal & Difficult Points Focal Points：1. Important new words, phrases and their usages, especially the theme-related telecom terms and expressions in the text;. 2. Organization of the text; 3. Translation training Difficult Points：1. Detailed analysis of difficult sentences in the text; 2. the attributive clause.  Teaching Methods Applied Ways of lecturing, multimedia demonstration and speech interacting are applied to achieve the most understanding of the text intended.  Discussion, Exercises and Assignments Discussion：The development of switching techniques Exercises：Exercises 1-2 Assignments： 1. to collect the materials related to switching techniques. 2. exercises 3-5 of page 132-135  Bibliography Zhang Daozhen,ed.Practical English Grammar (the 3rd Revision).Shanghai: the Commercial Press,1992 Shanghai Translation Publishing House,ed.New English-Chinese Dictionary. Shanghai:Shanghai Translation Publishing House,1988. Posts and Telecom Press,ed. English-Chinese Telecommunications Technology Dictionary.Beijing: Posts and Telecom Press,1997 Zhang Xiaohua and Shi Fangwen,ed.English for Telecommunications (the 4th Version).Beijing: Beijing University of Posts and Telecommunications Press,2004 Xu Xiulan.English for Computers and Telecommunications (the 3rd Revision) .Beijing: Beijing University of Posts and Telecommunications Press,2004  Teaching Content Contents Time Teaching Apparatuses  I. Revision Teacher uses the following exercise to help the students to revise the important expressions or phrases or sentences which were learnt in the study of last unit. Teacher : When I say a phrase or an expression in Chinese, you respond by giving an English equivalent your learnt in the study of Unit 2 Asynchronous Serial Data Transmission. Teacher ( Chinese ) Students ( English) 个人通信 personal communications 通信标准 communication standards 固定电话业务 fixed telephone service 网络容量 network capacity 移动交换中心 mobile switching center 国际漫游 international roaming 宽带业务 broadband services 接口转换 interface conversion 频谱分配 frequency allocation 模拟方式 analogue mode 蜂窝通信原理 cellular communication principle 基站 base station 突发脉冲传输方式 burst transmission mode 接入方法 access method 收费功能 billing function 切换算法 handover algorithms 短消息服务 short message service 技术规范 technical specification II. Pre-reading Activities Ask the Ss the following two questions related to the theme of the text: Can you enumerate what you contacted in the study of the courses including Switching? Possible answers: Circuit Switching and Packet Switching . Can you enumerate the trait of Circuit Switching and Packet Switching? Possible answers: The circuit is set up by a special signaling message that finds its way through the network, seizing channels in the path as it proceeds. ?A variation of message switching is packet switching. Here the message is broken up into several pieces of a given maximum length, called packets. As with message switching, each packet contains a header and a checksum. Packets are transmitted independently in a store-and-forward manner III. While-reading Activities i. New words and phrases Students read the new words and phrases aloud one by one after teacher.( 3 minutes) ii. Text organization 1. Ss read the text and point out the main idea of the text. The main idea: The text mainly discusses the trait of Circuit Switching and Packet Switching 2. Ss make an analysis of the organization of the text . The text may be divided into four major sections. Section1 (Lines1-12): the principle of Circuit Switching; Section2 (Lines13-35): the principle of Packet Switching Section3(Lines36-76): the predominance of Packet Switching iii. Key language points 1.本篇课文涉及到交换领域，题目circuit switching and packet switching可译为:“电路交换与分组交换”. 2. In circuit switching, a total path of connected lines is set up from the origin to the destination at the time the call is made, and the path remains allocated to the source-destination pair (whether used or not) until it is released by the communicating parties在电路交换中，当呼叫发生时，由呼叫源点到终点之间要建立整个通路的连线，而且在通信双方释放该电路之前，此通路一直保持分配给这对源点一终点(不管通路是否使用)。本句中的the call is made是一个定语从句，修饰the time，可译成:呼叫(被作出)的时候.allocated系过去分词，在句中作形容词用. 3. The switches, called circuit switches (or office exchange in telephone jargon), have no capability of storing or manipulating user's data on their way to the destination. 被称为电路交换机(或以电话行业用语称之为局交换)的交换设备没有存储或控制用户送往终点路由数据的能力。句中的storing和manipulating均为动名词形式，user's data系它们的动词宾语. 4. The circuit is set up by a special signaling message that finds its way through the network, seizing channels in the path as it proceeds. 电路由特殊的信令建立，该信令通过网络选择路由，并在其进程中确定信道。句中的seizing为现在分词，它作为动词finds的伴随情况. 5. ?In message switching, the transmission unit is a well-defined block of data called a message. In addition to the text to be transmitted, a message comprises a header and a checksum. 在报文交换中，传输单元是一个被精心定义的数据块，该数据块称为报文。to be transmitted为动词不定式的被动态，修饰 text，可译成:要传的内容. 6. The header contains information regarding the source and destination addresses as well as other control information; 报头含有源地址和目的地 址的信息，以及其他的控制信息 regarding系现在分词，修饰information,可译为:有关信源和目的地地址的信息. 7. The switching element is a computer referred to as a message processor, 交换单元是一台被 称为报文处理器的计算机referred to as …系过去分词短语，作computer的定语，可译为:被称作报文处理器的计算机. 8. Messages travel independently and asynchronously, finding their own way from source to destination. 报文独立并异步地传 输，在源点与终点间选择自己的传送路由。finding 系现在分词，作为动词travel的伴随情况. 9. First the message is transmitted from the host to the message processor to which it is attached首先报文由主机送往与之相连的报文处理机。to which中的which代表message processor，它引起一个定语从句，其中的to是动词attach的要求.从to which开始可译为:它被连接到的(报文处理器). 10. Once the message is entirely received, the message processor examines its header, and accordingly decides on the next outgoing channel on which to transmit it. 一旦报文被完全收到，报文处理机就检查其报头，并相应地决定该 报文传送的下一个输出信道。on which 中的which代表前面的channel. 11. This transmission technique is also referred to as the store-and-forward transmission technique. 这种传送技术亦被称为存储转发传输技术。store-and-forward:存储转发. 12. As with message switching与报文交换一样as with…就像……一样. 13. With circuit switching, there is always an initial connection cost incurred in setting up the circuit. 在电路交换的情况下，建立电路总要对开始的接续付出代价。incurred系过去分词，作形容词用.修饰cost，可译成:(所)经起的……. 14. It is cost-effective only in those situations where once the circuit is set up there is a guaranteed steady flow of information transfer to amortize the initial cost. 只有在这种情况下，即一旦电路建立后，信息的传送确保持续，源源不断，以便分摊初始花费，才能提高价格效率比to amortize the initial cost 是动词不定式短语，表示目的，可译成:以便缓冲初始费用. 15. Burstiness is a result of the high degree of randomness encountered in the message-generation process and the message size, and of the low delay constraint required by the user. 突发性是报文产生过程和报文长度高度的随机性所造成的，也是用户对时延要求很短造成的结果。在本句中，encountered in…size系过去分词短语，作定语，修饰the high degree of randomness,可译成:在……(方面)所遇到的高度随机性. 16. If a fixed dedicated end-to-end circuit were to be set up connecting the end users, then one must assign enough transmission bandwidth to the circuit in order to meet the delay constraint with the consequence that the resulting channel utilization is low如果要建立一个固定的专用的端到端电路以连接两个用户, 则必须对该电路分配足够的传输带宽以合平对时延的要求，其结果是电路的利用率很低。句中connecting the end users系现在分词短语，该现在分词在句中作状语，表示目的.逗点前的整个句子可译为:如果要建立一个固定专用的端到端电路以连接两端的用户 ; with the consequence that……可译为:其结果为…….. 17. If the circuit of high bandwidth were set up and released at each message transmission request, then the set-up time would be large compared to the transmission time of the message, resulting again in low channel utilization.如果对每个报文传输要求都要建立和释放大带宽的电路，则年报文传输的时间相比，电路建立的时值将很大，造成很低的电路利用率。resulting…为现在分词短语，该短语在句中作状语，表示结果，可译为:亦造成了很低的电路利用率. 18. Needless to say, packet switching presents design problems of its own, such as the need to recover packets of a given message that may arrive at the destination node out of sequence当然，分组交换亦有它自己设计上的麻烦，例如当报文无序地到达目的节点时，需要重新对该报文进行分组排序。 needless to say :不用说，当然.; need to reorder 中的动词不定式to reorder 作need的定语，可译为:重新排序的必要. 19. 与本单元课题有关的电信术语或用语：电路交换 circuit switching 分组交换 packet switching 报文交换 message switching 子网 subnet 信头 header 目的地址 destination address误差控制 error control 存储转发方式 store-and-forward manner 突发性 bursty 传输时延 transmission delay 中间交换设备 intermediate switching equipment交换技术 switching technique 返回信号 return signal 报文处理机 message processor 给定最大长度 given maximum length信息转移 information transfer 随机性random专用电路 dedicated circuit 电路利用率 channel utilization IV. Post-reading Activities i. Review the important expressions , phrases or sentences which were learnt in the study of text by guiding the students through Exercises 1-2 between Page 41 and Page 42 in class . ii. Ask the students to summarize the translation skills touched upon in the study of the text. Possible answers: 非谓语动词的使用和译法 V. Further Development of the Theme-related Specialized Knowledge 交换技术的发展及应用： http://www.sta.net.cn/article/fenzu/fenzu.html http://www.ddvip.com/netyl/Switch/index1/21.htm VI. Assignments 1．Preview Unit 12 2. Do Exercises3-5 between Page 132－135 3 mins 5 mins 3 mins 15 mins 45mins 15mins 3 mins 1 mins computer， projector， loud speaker blackboard，