通信英语 I单项选择 1.抽样频率 a. sampling rate b. repetition rate c. sampling frequency 答案:c 2.数字通信 a. digital communication b. digital transmission c. transmission th 答案 3.帧格式 a. synchronization word b. frame format c. reverse operation 答案:b 4.噪声功率 a. noisy environment b. signal levels c. noise power 答案:c 5.含噪声的环境 a. signal levels b. noisy environment c. noise power 答案:b 6.模拟信号 a. speech channel b. analog signal c. amplitude value 答案:b 7.脉冲流 a. stream of pulses b. receiving terminal c. terrestrial system 答案 8.传输路由 a. transmission path b. transmission quality c. binary transmission 答案 9.互联网 a. network resource Internet c. interconnected systems 答案:b 10.命令 a. copy b. host c. command 答案 11.拷贝 a. address b. mouse c. copy 答案:c 12.搜索工具 a. user interface b. searching tools c. electronic mail 答案:b 存取 a. access b. protocol c. copy
通信英语 I 单项选择 1．抽样频率 a. sampling rate b. repetition rate c. sampling frequency 答案：c 2．数字通信 a. digital communication b. digital transmission c. transmission path 答案：a 3．帧格式 a. synchronization word b. frame format c. reverse operation 答案：b 4．噪声功率 a. noisy environment b. signal levels c. noise power 答案：c 5．含噪声的环境 a. signal levels b. noisy environment c. noise power 答案：b 6．模拟信号 a. speech channel b. analog signal c. amplitude value 答案：b 7．脉冲流 a. stream of pulses b. receiving terminal c. terrestrial system 答案：a 8．传输路由 a. transmission path b. transmission quality c. binary transmission 答案：a 9．互联网 a. network resource b. Internet c. interconnected systems 答案：b 10． 命令 a. copy b. host c. command 答案：c 11． 拷贝 a. address b. mouse c. copy 答案：c 12． 搜索工具 a. user interface b. searching tools c. electronic mail 答案：b 13． 存取 a. access b. protocol c. copy
答案 14.网络资源 a. textual messages b. remote terminals c. network resources 答案 15.文本信息 a. information services hypertext protocol c. textual messages 答案:c 频谱 a. bandwidth b. spread spectrum c. frequency band 答案:b 17.移动手机 a. mobile subscriber b. mobile unit c. service performance 答案:b 18.频带 a. frequency spectrum b. frequency band c. spread spectrum 答案:b 蜂窝交换机 a. cellular switch b. cellular site c. mobile unit 答案 单边带 a. single-sideband b. bandwidth c. service area 答案:a 21.服务区 a. service area b. service performance c. service capabilit 答案:a 22.移动用户 a. mobile unit b. mobile subscriber c. mobile transceiver 答案:b 微处理器 a. subsystems b. utilization c. microprocessor 答案 24.无线机架 a. radio cabinet b. antenna c. mobile unit 答案 电路交换 a. packet switching b. circuit switching c. message switching 答案 分组交换 a. packet switching b. circuit switching C. message switching 答案 报文交换 a. packet switching b. circuit switchin message switchi 答案
答案：a 14． 网络资源 a. textual messages b. remote terminals c. network resources 答案：c 15． 文本信息 a. information services b. hypertext protocol c. textual messages 答案：c 16． 频谱 a. bandwidth b. spread spectrum c. frequency band 答案：b 17． 移动手机 a. mobile subscriber b. mobile unit c. service performance 答案：b 18． 频带 a. frequency spectrum b. frequency band c. spread spectrum 答案：b 19． 蜂窝交换机 a. cellular switch b. cellular site c. mobile unit 答案：a 20． 单边带 a. single-sideband b. bandwidth c. service area 答案：a 21． 服务区 a. service area b. service performance c. service capability 答案：a 22． 移动用户 a. mobile unit b. mobile subscriber c. mobile transceiver 答案：b 23． 微处理器 a. subsystems b. utilization c. microprocessor 答案：c 24． 无线机架 a. radio cabinet b. antenna c. mobile unit 答案：a 25． 电路交换 a. packet switching b. circuit switching c. message switching 答案：b 26． 分组交换 a. packet switching b. circuit switching c. message switching 答案：a 27． 报文交换 a. packet switching b. circuit switching c. message switching 答案：c
28.专用电路 a. dedicated circuit b. error control c. return signal 答案 突发性 a. bursty b. random c. header 答案:a 30.传输时延 a. destination address b. transmission delay c. return signal 答案:b 31.中间交换设备 a. given maximum b. intermediate switching equipment c. store-and-forward manner 答案:b 子网 答案 33.公众电信网 a. public telecommunication network b. intermediate switching node c. circuit- switched network 答案 4.半双工的 a. full-duplex b. half-duplex c. external call 答案:b 35.端局 a. toll center b. end office c. tandem switch 答案:b 36.外部呼叫 a. external call b. data traffic c. toll center 答案 37.链路 a. trunk b. link c. route 答案:b 38.交换节点 a. intermediate switching node b. voice-frequency circuit tching node 答案 39.音频电路 a. telephone subscriber b. voice-frequency circuit c. two wire connection 答案:b 40.拓扑 a. internodes b. topology c. route 答案:b
28． 专用电路 a. dedicated circuit b. error control c. return signal 答案：a 29． 突发性 a. bursty b. random c. header 答案：a 30． 传输时延 a. destination address b. transmission delay c. return signal 答案：b 31． 中间交换设备 a. given maximum b. intermediate switching equipment c. store-and-forward manner 答案：b 32． 子网 a. header b. subnet c. busty 答案：b 33. 公众电信网 a. public telecommunication network b. intermediate switching node c. circuit- switched network 答案：a 34.半双工的 a. full-duplex b. half-duplex c. external call 答案：b 35. 端局 a. toll center b. end office c. tandem switch 答案：b 36. 外部呼叫 a. external call b. data traffic c. toll center 答案：a 37.链路 a. trunk b. link c. route 答案：b 38.交换节点 a. intermediate switching node b. voice-frequency circuit c. switching node 答案：c 39.音频电路 a. telephone subscriber b. voice-frequency circuit c. two wire connection 答案：b 40.拓扑 a. internodes b. topology c. route 答案：b
41.二线连接 a. data traffic b. end office c. two wire connection 答案 42.数据流量 a. data traffic b. tandem switch center 答案 43.全球通信 a. interface equipment b. global communication c. communication carriers 答案:b 44.脉码调制 a. pulse code modulation b. voice encoding c. open network 答案: 接口设备 a. switching equipment transmission medium c. interface equipment 答案:c 46.综合业务数字网 0 end-to-end digital connectivity b. international organization for standardization c. integrated services digital network 答案 47.通信载体 a. communication carriers b. transmission medium c. interface equipment 答案 48.系统结构 L. infrastructure c. flexibility d. basic access 答案 a 49.蜂窝式移动电话 a. cellular switch b. cellular mobile telephone c. cellular site 答案:b 50.数据传输 a. data transmission b. transmission error c. error flag 答案 51.传号电平 a. space level b. logical level C. mark level 答案:c 52.接收机的定时 a. intersymbol space b. serial interface c. receiver timing 答案:c 53.明显的缺点 a. transmission error b. obvious disadvantage
41.二线连接 a. data traffic b. end office c. two wire connection 答案：c 42.数据流量 a. data traffic b. tandem switch c. toll center 答案：a 43.全球通信 a. interface equipment b. global communication c. communication carriers 答案：b 44.脉码调制 a. pulse code modulation b. voice encoding c. open network 答案：a 45.接口设备 a. switching equipment b. transmission medium c. interface equipment 答案：c 46.综合业务数字网 a) end-to-end digital connectivity b. international organization for standardization c. integrated services digital network 答案：c 47.通信载体 a. communication carriers b. transmission medium c. interface equipment 答案：a 48.系统结构 a. infrastructure c. flexibility d. basic access 答案：a 49.蜂窝式移动电话 a. cellular switch b. cellular mobile telephone c. cellular site 答案：b 50.数据传输 a. data transmission b. transmission error c. error flag 答案：a 51.传号电平 a. space level b. logical level c. mark level 答案： c 52.接收机的定时 a. intersymbol space b. serial interface c. receiver timing 答案：c 53.明显的缺点 a. transmission error b. obvious disadvantage
C. error flag 答案:b 54.起始位 a. start bit b. stop bit c. parity bit 答案 空号电平 a. mark level b. space level c. the idle state 答案 56.控制比特 binary data b. local clock c. control bit 答案 57.串行接口 a. data stream b. Crt terminal c. serial interface 答案 58.发送器和接收器 a. transmitter and receiver b. receiver timing c. duration of t seconds 答案:a 59.二进制数据 答案: y data b. data stream c. data transmission a. bina 60.高速电子开关 a. the voice channel b. the repetition rate high-speed switch 答案:c II.根据所给英文选择合适的答案 1. digital communication a.全球通信b.公共通信载体c.数字通信 答案 2. voice encoding techniques a.语音编码技术b.脉冲c.脉冲编码调制 答案:a 3. basic access signaling rate a.大量的接口设备 b.基本接入信令速率 C.统一的接入 答案:b 4. the International Organization for Standardization a.综合业务数字网b.ISDN的标准和系统结构c.国际标准化组织 答案 5. end-to-end digital connectivity a.基本接入信令速率b.端对端的数字连接 C.语音编码技术 答案:b 6. progressive application of digital technology
c. error flag 答案：b 54. 起始位 a. start bit b. stop bit c. parity bit 答案：a 55.空号电平 a. mark level b. space level c. the idle state 答案：b 56.控制比特 a. binary data b. local clock c. control bit 答案：c 57.串行接口 a. data stream b. CRT terminal c. serial interface 答案：c 58.发送器和接收器 a. transmitter and receiver b. receiver timing c. duration of T seconds 答案：a 59.二进制数据 a. binary data b. data stream c. data transmission 答案：a 60.高速电子开关 a. the voice channel b. the repetition rate c. a high-speed switch 答案：c II.根据所给英文选择合适的答案 1． digital communication a.全球通信 b. 公共通信载体 c.数字通信 答案：c 2． voice encoding techniques a.语音编码技术 b. 脉冲 c. 脉冲编码调制 答案：a 3． basic access signaling rate a.大量的接口设备 b. 基本接入信令速率 c. 统一的接入 答案：b 4． the International Organization for Standardization a.综合业务数字网 b. ISDN 的标准和系统结构 c. 国际标准化组织 答案：c 5． end-to-end digital connectivity a. 基本接入信令速率 b.端对端的数字连接 c. 语音编码技术 答案：b 6． progressive application of digital technology
由于传输媒体导致的质量下降 b.4KHz话路中所固有的带宽限制 C.数字技术的逐步应用 答案 7. enhanced quality a.高质量 b.带宽的限制 C.统一的接入 答案:a 8. the branches between nodes a.节点间的支路b.中间交换节点c.全双工的连接 答案:a 9. tree topology a.双绞线 b.结构部件 树状拓扑 答案 backbone hierarchical network 国家网络b.被分离开的子网c.主干体系网络 答案:c the subscriber that transmit digital signal 发送数字信号的用户b.一小部分用户c.相邻的端局 答案 12. multiple voice-frequency circui a.高效中继线 b.多音频电路 C.同步时分复用 答案:b 13. the function of concentrating traffic a.集中话务量的功能b.路由选择的基本次序 C.发送数字信号的用户 答案 14. full duple a.全双工的连接 b.全连通性 C.全双工的 答案 transmission facilitie 传输设备 b.交换区 C.高效中继线 16. switching technique a.交换技术 b.电路交换 C.分组交换 答案 tching a.交换技术 b.报文交换 C.分组交换 答案:b communication parties a.传输单元 b.通信各方 C.返回信号 答案:b the special signaling message a.存储转发传输技术b.带宽的动态分配c.特定的信令信息 答案:c
a. 由于传输媒体导致的质量下降 b. 4KHz 话路中所固有的带宽限制 c. 数字技术的逐步应用 答案：c 7． enhanced quality a.高质量 b. 带宽的限制 c.统一的接入 答案：a 8． the branches between nodes a.节点间的支路 b. 中间交换节点 c. 全双工的连接 答案： a 9． tree topology a. 双绞线 b. 结构部件 c. 树状拓扑 答案：c 10． backbone hierarchical network a. 国家网络 b. 被分离开的子网 c. 主干体系网络 答案：c 11． the subscriber that transmit digital signal a. 发送数字信号的用户 b. 一小部分用户 c. 相邻的端局 答案：a 12． multiple voice-frequency circuits a. 高效中继线 b. 多音频电路 c. 同步时分复用 答案：b 13． the function of concentrating traffic a.集中话务量的功能 b. 路由选择的基本次序 c. 发送数字信号的用户 答案：a 14． full duplex a. 全双工的连接 b. 全连通性 c. 全双工的 答案：c 15． transmission facilities a. 传输设备 b. 交换区 c. 高效中继线 答案：a 16． switching technique a.交换技术 b. 电路交换 c. 分组交换 答案：a 17． message switching a.交换技术 b. 报文交换 c. 分组交换 答案：b 18． communication parties a.传输单元 b. 通信各方 c. 返回信号 答案：b 19． the special signaling message a. 存储转发传输技术 b. 带宽的动态分配 c. 特定的信令信息 答案：c
20. low channel utilization 低的电路利用率b.报文整个的传输时延C.传输单元 答案 21. total path of connected lines a.连线的整个通路b.源到目的地的一对c.带宽的动态分配 答案:a radio cabinet a.无线通信行业 无线机架 C.多径衰耗 答案:b 23. telephone company zone offices a.移动收发信机 b.电话公司地方局C.中央协调单元 答案:b available radio frequency spectrur 所分配的频带 b.调频广播业务 C,可用的无线电频谱 答案:c central coordinating element a.中央协调单元 b.试验性的蜂窝系统 C.有限的服务能力 答案:a severe spectrum limitations 严厉的频谱限制b.有限的服务能力 C.有限的指定频带 答案:a developmental cellular system a.频谱利用率b.试验性的蜂窝系统c.传统移动电路的运行限制 答案:b 8. propagation path loss a.调频广播业务b.传输路径衰耗c.无线机架 答案:b backbone system a.主干系统b.电子会议c.远程终端 答案 live conversation .最大的信息库b.文本信息C.实时的对话 答案:c 31. textual messages a.搜索工具b.万维网 文本信息 答案 32. the networked hypertext protocol a.联网的超文本协议b.网络设备资源 全国范围的网络 答案:a the Unix operating system a.主干系统b.万维网c.Unix操作系统 答案 34. the vast ma jority of the computers on the net
20． low channel utilization a. 低的电路利用率 b. 报文整个的传输时延 c. 传输单元 答案：a 21． total path of connected lines a. 连线的整个通路 b. 源到目的地的一对 c. 带宽的动态分配 答案：a 22． radio cabinet a. 无线通信行业 b. 无线机架 c. 多径衰耗 答案：b 23． telephone company zone offices a.移动收发信机 b. 电话公司地方局 c. 中央协调单元 答案：b 24． available radio frequency spectrum a. 所分配的频带 b. 调频广播业务 c. 可用的无线电频谱 答案：c 25． central coordinating element a. 中央协调单元 b. 试验性的蜂窝系统 c. 有限的服务能力 答案：a 26． severe spectrum limitations a.严厉的频谱限制 b. 有限的服务能力 c. 有限的指定频带 答案：a 27． developmental cellular system a. 频谱利用率 b. 试验性的蜂窝系统 c. 传统移动电路的运行限制 答案：b 28． propagation path loss a. 调频广播业务 b. 传输路径衰耗 c. 无线机架 答案：b 29． backbone system a.主干系统 b. 电子会议 c. 远程终端 答案：a 30． live conversation a.最大的信息库 b. 文本信息 c. 实时的对话 答案：c 31． textual messages a.搜索工具 b. 万维网 c. 文本信息 答案：c 32． the networked hypertext protocol a.联网的超文本协议 b. 网络设备资源 c. 全国范围的网络 答案：a 33． the Unix operating system a. 主干系统 b. 万维网 c. Unix 操作系统 答案：c 34． the vast majority of the computers on the net
a.在网上的绝大多数计算机b.分布在全世界的计算机的巨大网络 全国范围的网络 答案 remote terminal a.电子会议b.远程终端c.文本信息 答案:b the largest repository of information a.最大的信息库b.实时的对话c.方便的搜索工具 答案 the time division multiplexer a.时分多路复用b.高速的电子开关c.时分多路复用器 答案 38. A high-speed electronic switch a.高速的电子开关b.被传信号的波形C.时分多路复用 答案:a time Division Multiplexing a.时分多路复用b.时分多路复用器 地面系统 答案 the presence or absence of the pulse a.一串幅值b.每样值8位码c.脉冲的“有”或“无” 答案 4 the unique or absence of the pulse a.脉冲的“有”或“无” b.被称为同步字的独特的码序列 C.将抽样的幅值转换成一串脉冲的单元 答案:b A sequence relating to channell, 2 and so on 涉及到第一路、第二路及其他各路的序列 b.一条特定消息中的全部信号 理论上的最小采样频率 答案:a the schemes for performing these three functions a.电话质量的话路b.由卫星上收到的信号c.实现这三项功能的 方案 答案 a series of amplitude values a.一串幅值b.被传信号的波形c.每样值8位码 答案 45. A speech channel of telephone quality a.实现这三项功能的方案b.将抽样的幅值转换成一串脉冲的单元 C.电话质量的话路 答案 A sequence of 8-binary digits 每样值8位码 个8位二进制序列c.一串幅值 答案:b
a.在网上的绝大多数计算机 b. 分布在全世界的计算机的巨大网络 c. 全国范围的网络 答案：a 35． remote terminal a. 电子会议 b. 远程终端 c. 文本信息 答案：b 36． the largest repository of information a. 最大的信息库 b. 实时的对话 c. 方便的搜索工具 答案：a 37． the time division multiplexer a. 时分多路复用 b. 高速的电子开关 c. 时分多路复用器 答案：c 38． A high-speed electronic switch a. 高速的电子开关 b. 被传信号的波形 c. 时分多路复用 答案：a 39． time Division Multiplexing a. 时分多路复用 b. 时分多路复用器 c. 地面系统 答案：a 40． the presence or absence of the pulse a. 一串幅值 b. 每样值 8 位码 c. 脉冲的“有”或“无” 答案：c 41． the unique or absence of the pulse a. 脉冲的“有”或“无” b. 被称为同步字的独特的码序列 c. 将抽样的幅值转换成一串脉冲的单元 答案：b 42． A sequence relating to channel1, 2 and so on a. 涉及到第一路、第二路及其他各路的序列 b. 一条特定消息中的全部信号 c. 理论上的最小采样频率 答案：a 43． the schemes for performing these three functions a. 电话质量的话路 b. 由卫星上收到的信号 c. 实现这三项功能的 方案 答案：c 44． a series of amplitude values a.一串幅值 b. 被传信号的波形 c. 每样值 8 位码 答案：a 45． A speech channel of telephone quality a. 实现这三项功能的方案 b. 将抽样的幅值转换成一串脉冲的单元 c. 电话质量的话路 答案：c 46． A sequence of 8-binary digits a. 每样值 8 位码 b. 一个 8 位二进制序列 c. 一串幅值 答案：b
47. A minimum theoretical sampling frequency a.理论上的最小采样频率b.抽样量化和编码 C.将抽样的幅值转换成一组脉冲的单元 答案 48. the sparking of a car ignition system a.高速电子开关b.理论上的最小采样频率 C.汽车点火系统的打火 答案:c 49. the stream of the pulses with a repetition rate of 64KHz 真实信号与噪声信号的关系b.由传输路由引入的衰减 C.重复率为64KHz的脉冲流 答案 the relationship of the true signal to the noise signal a.真实信号与噪声信号的关系b.脉冲的有和无 C.被称为同步字的独特的码序列 答案 terrestrial system 高速电子开关b.地面系统 时分多路复用 答案:b asynchronous serial data transmission a.数据链路面向字符的特征b.异步串行数据传输 C.异步串行接口 答案:b solated subnetworks 被分离的子网b.高效中继线c.交换区 答案: 54. two subscribers attached to different end offices 在站和网络之间的接口b.路由选择的基本次序 C.连到不同端局的两个用户 答案:c synchronous TDM a.同步时分复用 多条音频电路c.节点间的之路 答案:a 56. the clocks at the transmitter and receiver 符号间空格持续时间的三倍b.在字符后所收到的奇偶校验位 发送器和接收器时钟 答案:c 57. the transmitted data a.电传机时代b.一个字符的点和划C.所发送的数据 答案 the falling edge of the start bit a.起始位的下降沿b.停止位的下降沿c.电传机时代 答案: 59. the group of bits called characters
47． A minimum theoretical sampling frequency a. 理论上的最小采样频率 b. 抽样量化和编码 c. 将抽样的幅值转换成一组脉冲的单元 答案：a 48． the sparking of a car ignition system a. 高速电子开关 b. 理论上的最小采样频率 c. 汽车点火系统的打火 答案：c 49． the stream of the pulses with a repetition rate of 64KHz a. 真实信号与噪声信号的关系 b. 由传输路由引入的衰减 c. 重复率为 64KHz 的脉冲流 答案:c 50． the relationship of the true signal to the noise signal a. 真实信号与噪声信号的关系 b. 脉冲的有和无 c. 被称为同步字的独特的码序列 答案：a 51． terrestrial system a. 高速电子开关 b. 地面系统 c. 时分多路复用 答案：b 52． asynchronous serial data transmission a. 数据链路面向字符的特征 b. 异步串行数据传输 c. 异步串行接口 答案：b 53． isolated subnetworks a. 被分离的子网 b. 高效中继线 c. 交换区 答案：a 54． two subscribers attached to different end offices a. 在站和网络之间的接口 b. 路由选择的基本次序 c. 连到不同端局的两个用户 答案：c 55． synchronous TDM a. 同步时分复用 b. 多条音频电路 c. 节点间的之路 答案：a 56． the clocks at the transmitter and receiver a. 符号间空格持续时间的三倍 b. 在字符后所收到的奇偶校验位 c. 发送器和接收器时钟 答案：c 57． the transmitted data a. 电传机时代 b. 一个字符的点和划 c. 所发送的数据 答案：c 58． the falling edge of the start bit a. 起始位的下降沿 b. 停止位的下降沿 c. 电传机时代 答案：a 59． the group of bits called characters
a.数据链路面向字符的特征b.在字符后所收到的奇偶校验位 被称为字符的比特组 答案:c 60. A clock generated locally by the receiver a.最为流行的串行接口b.由接收机本地产生的时钟 C.发送器和接收器的时钟 答案:b III.选择合适的答案 1. Furthermore, we shall prove that a minimum theoretical sampling frequency of order 6 8KHz is required() a voice channel()the range 300 Hz to 3. 4KHz a convey, occupy b. to convey, occupying c. conveying, occupied d. convey, to occupy 答案:b 2. For example, the signal( from a satellite,()in far outer space, is very weak. a. received, located b. receive, locate c. receiving, locating d. to receive, to located 答案:a 3. If we consider binary transmission, the complete information about a particular message will always( by simply( )the presence or absence of the pulse. a. obtain, detect b. be obtained, detecting obtained, detected d. obtaining, detected 答案:b 4. There is a inherent advantage for() noisy environments by() digital transmission a. overcoming, choose b. overcome, choosing c. overcome, choose d. overcoming, choosing 答案:d 5. Each voice channel has a separate coder, the unit( converts sampled amplitude values to a set of pulse; and decoder, the unit( )performs the reverse operation. a, who, who b. when. when c. where. where d. that, that 答案:d 6. The problem is easily overcome by( )a frame format, where at the start of each frame a unique sequence of pulses is placed () the start of the frame a. specify, identify b. specifying, so as to identify c. specified, identified d. specify, identifying 答案:b 7. It was( ) in 1969, when the U. S. Department of Defense established
a. 数据链路面向字符的特征 b. 在字符后所收到的奇偶校验位 c. 被称为字符的比特组 答案：c 60． A clock generated locally by the receiver a. 最为流行的串行接口 b. 由接收机本地产生的时钟 c. 发送器和接收器的时钟 答案：b III.选择合适的答案 1.Furthermore, we shall prove that a minimum theoretical sampling frequency of order 6.8KHz is required ( ) a voice channel ( ) the range 300 Hz to 3.4KHz. a. convey , occupy b. to convey, occupying c. conveying , occupied d. convey, to occupy 答案：b 2. For example, the signal ( ) from a satellite, ( ) in far outer space, is very weak. ａ. received, located b. receive, locate c. receiving, locating d. to receive, to located 答案：a 3. If we consider binary transmission, the complete information about a particular message will always ( ) by simply ( ) the presence or absence of the pulse. ａ.obtain, detect b. be obtained, detecting c. obtained, detected d. obtaining, detected 答案：ｂ 4. There is a inherent advantage for ( ) noisy environments by ( ) digital transmission. ａ．overcoming, choose b. overcome, choosing c. overcome, choose d. overcoming , choosing 答案：d 5. Each voice channel has a separate coder, the unit ( ) converts sampled amplitude values to a set of pulse; and decoder, the unit ( ) performs the reverse operation. ａ．who, who b. when, when c. where, where d. that , that 答案：d 6. The problem is easily overcome by ( ) a frame format, where at the start of each frame a unique sequence of pulses is placed ( ) the start of the frame. a. specify, identify b. specifying, so as to identify c. specified, identified d. specify, identifying 答案：b 7. It was ( ) in 1969, when the U.S. Department of Defense established