Chapter Three Data Communications Unit8 a part 1 Notes to Text L Part4 Extensive Reading Part 2 Word Study Part5 Notes to Passage Part3 Practice on Text Part6 Practice on Passage 2021/2/20 P1
2021/2/20 P.1 Unit 8 Data Communications Chapter Three @ Part 1 Notes to Text & Part4 Extensive Reading & Part 2 Word Study @ Part5 Notes to Passage @ Part3 Practice on Text @ Part6 Practice on Passage
a Part 1 Notes to text Data communications 1)"External"devices are generally thought of as being independently powered circuitry that exists beyond the chassis of a computer or other digital message source blHp 设备通常被认为是装有动力的独立电路系统,一般是安装在计算机 底盘或其它数据信息源底盘之下。 注释:介词短语 as being independently powered circuitry是主语 补足语。That引导的定语从句修饰先行词 circuitry 2) It is the aim of any communications system to provide the highest possible transmission rate at the lowest possible power and with the least possible noise.任何一个通信系统, 其目的就是要能够以仅最可能低的功率和最少的噪音提供最大可能 的传输速度。 注释:该句的主语是不定式 to provide the highest possible transmission rate at the lowest possible power and with the least possible noise 2021/2/20 P2
2021/2/20 P.2 @ Part 1 Notes to Text 1）"External" devices are generally thought of as being independently powered circuitry that exists beyond the chassis of a computer or other digital message source. 外部 设备通常被认为是装有动力的独立电路系统，一般是安装在计算机 底盘或其它数据信息源底盘之下。 注释：介词短语as being independently powered circuitry是主语 补足语。That引导的定语从句修饰先行词circuitry。 2）It is the aim of any communications system to provide the highest possible transmission rate at the lowest possible power and with the least possible noise. 任何一个通信系统， 其目的就是要能够以仅最可能低的功率和最少的噪音提供最大可能 的传输速度。 注释：该句的主语是不定式to provide the highest possible transmission rate at the lowest possible power and with the least possible noise。 Data Communications
3)The end equipment which either generates the digital information for transmission or uses the received digital data can be computers, printers, keyboards, CRTs, and so on. it 备可以是计算机、打印机、键盘、CRT等,它们可以生成要发送的 数字信息,也可以使用所接收的数字数据 注释:此句是典型的复合句;主语是 The end equipment;谓语动 词是 can be;whch引导显然是定语从句,修饰主语。 4) Digital data, when transmitted, are in serial form. Parallel transmission of an 8-bit word would require eight pairs of transmission lines- not at all cost-effective.数字数据在发送时 是串行的。并行发送一个8位的字需要8对传输线,这是不经济的。 注释:过去分次词短语 when transmitted是典型的时间状语;后 句中的破折号省略了 which is,即应为 which is not at all cost- effective,相当于一个非限制性定语从句,对前面作进一步说明 2021/2/20 P3
2021/2/20 P.3 3）The end equipment which either generates the digital information for transmission or uses the received digital data can be computers, printers, keyboards, CRTs, and so on. 端设 备可以是计算机、打印机、键盘、CRT等，它们可以生成要发送的 数字信息，也可以使用所接收的数字数据。 注释：此句是典型的复合句；主语是The end equipment；谓语动 词是can be；which 引导显然是定语从句，修饰主语。 4）Digital data, when transmitted, are in serial form. Parallel transmission of an 8-bit word would require eight pairs of transmission lines - not at all cost-effective. 数字数据在发送时 是串行的。并行发送一个8位的字需要8对传输线，这是不经济的。 注释：过去分次词短语when transmitted是典型的时间状语；后 句中的破折号省略了which is，即应为which is not at all costeffective，相当于一个非限制性定语从句，对前面作进一步说明
5) Data communications equipment (DCE)accepts the serial data stream from the dte and converts it to some form of analog signal suitable for transmission on voice-grade lines. 3 据通信设备(DCE)从DTE接收串行数据流,并将其转换成适合于在 话音线路上发送的某种模拟信号形式 注释:该句是简单句;主语DCE也称为数据电路终接设备Data Circuit-terminating Equipment;形容词短语 suitable for transmission on voice-grade lines. inform of analog signal 6)If you transmit data by digital channel(sometimes it is called Digital T-carrier"), a Pulse Code Modulation (PCM) equipment must be used.如果使用数字信道(有时称为数字T载波) 传输数据,则应使用脉码调制(PCM)设备。 注释: T-carrier源于美国贝尔公司的数字通信系统,将从音频频带上 来的信号转换成数字脉冲,沿金属线传送称为 T-carrier 2021/2/20 SPaY End
2021/2/20 P.4 5）Data communications equipment (DCE) accepts the serial data stream from the DTE and converts it to some form of analog signal suitable for transmission on voice-grade lines. 数 据通信设备（DCE）从DTE接收串行数据流，并将其转换成适合于在 话音线路上发送的某种模拟信号形式。 注释：该句是简单句；主语DCE也称为数据电路终接设备Data Circuit-terminating Equipment；形容词短语suitable for transmission on voice-grade lines.修饰form of analog signal。 6）If you transmit data by digital channel (sometimes it is called “Digital T-carrier”), a Pulse Code Modulation (PCM) equipment must be used. 如果使用数字信道（有时称为数字T载波） 传输数据，则应使用脉码调制（PCM）设备。 注释：T-carrier源于美国贝尔公司的数字通信系统，将从音频频带上 来的信号转换成数字脉冲，沿金属线传送称为T-carrier。 End
Part 2 Word Study 1. chassis n.底板;机箱 1l. synchronous adj,同步的 2. proportional adi成比例的12. multipoint adi.多点(式)的,多位置的 3. inversely adv.相反地 13. subscriber n.订户,用户 4. internally adv.内部地;在内部14. exclusive adj独一的,唯一的 5 parallel n.平行线:平行面15. property n.资产;占有物 6. cost-effective adj.划算的 16. voice-grade adj.话音级的 7 encompass v.包含;包括17. digital-to. analog ad.数字到模拟的 8 circuitry n电路(系统)18 quadrature n.正交 9. conversion n.转换,转化 19. amplitude n.振幅 10. asynchronous adj.异步的 P6上En
2021/2/20 P.5 End 1. chassis n. 底板；机箱 11. synchronous adj. 同步的 2. proportional adj. 成比例的 12. multipoint adj. 多点(式)的,多位置的 3. inversely adv. 相反地 13. subscriber n. 订户, 用户 4. internally adv. 内部地；在内部 14. exclusive adj. 独一的, 唯一的 5. parallel n. 平行线；平行面 15. property n. 资产；占有物 6. cost-effective adj. 划算的 16. voice-grade adj. 话音级的 7. encompass v. 包含；包括 17. digital-to-analog adj. 数字到模拟的 8. circuitry n. 电路（系统） 18. quadrature n. 正交 9. conversion n. 转换, 转化 19. amplitude n. 振幅 10. asynchronous adj. 异步的 & Part 2 Word Study