UNIT 1同位语跟在所修饰的名词之后，可表示相同的事物或人，也可对 该名词进行说明。同位语与所修饰的名词之间可以用各种标点符 号隔开，这时同位语可以对标点符号前的整个句子进行说明。PCM is dependent on three separate operations, sampling, quantizing, and coding.Substances fall into three groups: conductors, semiconductors and insulators.The laser is able to amplify light one unique property.(9 -4) can only be applied provided that the unsaturated gain coefficient exceeds the losses , a necessary requirement for oscillation.这里列举了同位语位于句尾，修饰最后一个名词或整个句子的情 况。还有其它的情况，课文中遇到时在讲。介词短语 for doing something 作后置定语，表示目的，意思为用 于的。Schemes for performing these three functions have evolved, and shall describe the main ones.algorithms for decoding received signals这里的 ones 是代词, 避免重复。A working equation expresses the unknown quantity in terms of the known ones.These equations are called differential equations, and now their study forms one of the most challenging branches of mathematics.We shall see how a speech channel be conveyed as a series of amplitude values, each value being represented as a sequence of 8 binary digits.分词短语出现在句尾，用逗号隔开，表示伴随 情况说明，非常常见。这时分词短语的逻辑主语经常省略。被省略的逻辑主语多数情况下指的是主句的主 语或逗号前整个句子的含义，点也有少数列外 。具体情况以后结合课文讲解。It is that (which, when, who) 强调句型，如It is the document that is very important.It was Faraday who first discovered electromagnetic induction.known as the signal-to-noise ratio 过去分词短语作 后置定语，常见，译为 称之为。of the most interest to , 对最感兴趣的of interest = interesting of importance = important 名词逗号同位语+逗号 进行说明 An American, Edison, invented the first small electric lamp. g, the acceleration of gravity at the earths surface, has the value 32 ft/sec2.1. 正是数字传输为克服这种噪声环境提供了一种有力的方法 。2. 数字传输正是对于克服这种噪声环境提供了一种有力的方 法。3. 最高频率为3.4kHz的话音信号是用64kHz的信号来表示的， 这是一个我们昨天所学的事实。4. 编码器是将采样幅值转换成一组脉冲的单元，它对数字传 输是非常重要的。5. 编码的问题是一个极为重要的问题。6. PCM这个术语是一个通信术语。7. 每采样值8位（码）的重复速率比4位的重复速率高。8. 话音信号是一个模拟信号，通过采样、量化和编码，我们 可以实现话音信号的数字传输。汉译英练习：（除第8题外每题只用一个谓语动词）1. 正是数字传输为克服这种噪声环境提供了一种有力的 方法。 It is digital transmission that provides a powerful method for overcoming the noisy environment.2. 数字传输正是为克服这种噪声环境提供了一种有力的 方法。 It is for overcoming the noisy environment that digital transmission provides a powerful method.3. 最高频率为3.4kHz的话音信号是用64kHz的信号来表 示的，这是一个我们昨天所学的事实。The speech signal of maximum frequency 3.4kHz has been represented by a signal of frequency 64 kHz, a fact that we learned yesterday.4. 编码器是将采样幅值转换成一组脉冲的单元，它对 数字传输是非常重要的。The coder, a unit that converts amplitude values to a set of pulses, is very important to digital transmission.5. 编码的问题是一个极为重要的问题。The problem of coding is a very important one.6. PCM这个术语是一个通信术语。The term PCM is a communications one.7. 每采样值8位（码）的重复速率比4位的重复速率高 。The repetition rate of 8-digits per sample value is higher than that of 4-digits.8. 话音信号是一个模拟信号，通过采样、量化和编码 ，我们可以实现话音信号的数字传输。The speech signal is a analog one, and we can perform its digital transmission by sampling, quantizing and coding.UNIT 2部分否定与完全否定：对于集合中的个体，否定动词为部分否定，否定名词为完全否定。 Instruments here are not good. 这里的仪器并非都是好的。 No instruments here are good. 这里的所有仪器都不是好的。All the data are not to be checked. None of the data are to be checked. 所有的数据都不核对。并非所有数据都要核对。Both the transistors on the table are not good.桌子上两个晶体管并不都是好的。Neither of the transistors on the table are good.桌子上两个晶体管都不是好的。并列复合句中的省略：在并列复合句中，后一复合句中与前一复合句相重复 的部分可以省略。Matters consist of molecules and molecules of atoms.The earth attracts the moon and the moon the earth. The meter is the standard for length, the gram for weights.Electrons are injected into the P region, and holes into the N region.samples the next N bits at their centers, using a clockusing a clock generated locally by the receiver严格的语法修饰：分词作定语单个分词作定语，位于所修饰名词之前。分词短语作定语，位于所修饰名词之后。 moving electrons electrons moving within the wire the applied voltage the voltage applied across the resistance (易加修饰）the voltage applied by the circuit across the resistance to amplify the incoming signal used method （不易加修饰）commonly used methodthe most commonly used method英译汉练习：（要求用本课所学句型翻译）1. 字符中的比特位并非全部用于表示数据。2. 所有起始位都不被设定为信号电平。3. 我们将字符的起始位设置成空号电平，而将字符的 终止位设置成信号电平。4. 在计算机与其显示终端之间最为常见的串行接口是 异步串行接口，而在程控交换机与其电话终端之间 最为常见的串行接口是同步串行接口。5. 由发送器所送出的停止位总是被设置成信号电平。6. 现在我们来考虑一个包含12比特的字符。7. PCM是用以将模拟信号转换成数字信号的一种重要 方法。1. 字符中的比特位并非全部用于表示数据。All bits of a characters are not used to represent data.2. 所有起始位都不被设定为信号电平。No (None of) start bits are placed in the mark level.3. 我们将字符的起始位设置成空号电平，而将字符的 终止位设置成信号电平。The start bit of a character is placed in the space level, and the stop bit the mark level. 4. 在计算机与其显示终端之间最为常见的串行接口是 异步串行接口，而在电路交换机与其电话终端之间 最为常见的串行接口是同步串行接口。By far the most popular serial interface between a computer and its CRT terminal is the asynchronous serial interface, and between a circuit switch and its telephone terminal, the synchronous one. 5. 由发送器所送出的停止位总是被设置成信号电平。Stop bit send by transmitters are always placed in the mark level. 6. 现在我们来考虑一个包含8个信息比特加4个控制比特 的字符。Now consider a character consisting of 8 information bit plus 4 control bits.7. PCM是用以将模拟信号转换成数字信号的一种重要 方