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【简答题】
模拟电话话路的频带宽度为300～3400Hz，若要利用此信道传送二进制的数据信号需要接入调制解调器(MODEM)以适应信道通带要求，问MODEM在此完成了何种功能?请你试想一种可能实现MODEM系统的方案，画出简要的原理框图(假定数据信号的速率为1200bit/s，波形为不归零矩形脉冲)。
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Online services are managed by a host system that maintains a base of information available to satellite users. Users of so-called "dumb" terminals (i. e., those without processing capability)simply a...
A.
Online services are managed by a host system that maintains a base of information available to satellite users. Users of so-called "dumb" terminals (i. e., those without processing capability)simply access the information base via programs stored on the system. Personal computer (PC) users typically access the host through a modem (调制解调器). A PC software program serves as an intece (接口)between the server and a PC, allowing the user to operate through the online system and select different databases using a keyboard or a mouse.
B.
National and regional online systems usually have local telephone numbers that PC modems can call to access either a local information base or an indirect long-distance connection, thus reducing long-distance telephone fees. Some online systems allow users ’to copy large volumes of information onto a local memory storage device, which also reduces the time the user is connected to the online system.
C.
Besides offering a great number of different information based, ranging from full-text journal li- braries to reports of missing children, online services allow users to, for example, reserve airline tick- ets, buy stocks, purchase goods, and communicate with other users. In exchange for the service, users usually pay a monthly membership fee. They may also pay to connect to various databases on the service or to download information.
【单选题】ITU V90调制解调器(MODEM)______。
A.
下载速率是56kb/s，上传速率是33.6kb/s
B.
上下行速率都是56kb/s
C.
与标准X.25公用数据网连接，以56kb/s的速率交换数据
D.
时刻与ISP连接，只要开机，永远在线
【单选题】调制解调器(Modern)的作用是( )。
A.
将数字脉冲信号转换成模拟信号
B.
将模拟信号转换成数字脉冲信号
C.
将数字脉冲信号与模拟信号互相转换
D.
为了上网与打电话两不误
【单选题】调制解调器(Modem)的功能是。
A.
将数字信号转换成模拟信号
B.
将模拟信号转换成数字信号
C.
兼有A和B的功能
D.
使用不同频率的载波将信号变换到不同的频率范围
相关题目：
【单选题】Online services are managed by a host system that maintains a base of information available to satellite users. Users of so-called "dumb" terminals (i. e., those without processing capability)simply a...
A.
Online services are managed by a host system that maintains a base of information available to satellite users. Users of so-called "dumb" terminals (i. e., those without processing capability)simply access the information base via programs stored on the system. Personal computer (PC) users typically access the host through a modem (调制解调器). A PC software program serves as an intece (接口)between the server and a PC, allowing the user to operate through the online system and select different databases using a keyboard or a mouse.
B.
National and regional online systems usually have local telephone numbers that PC modems can call to access either a local information base or an indirect long-distance connection, thus reducing long-distance telephone fees. Some online systems allow users ’to copy large volumes of information onto a local memory storage device, which also reduces the time the user is connected to the online system.
C.
Besides offering a great number of different information based, ranging from full-text journal li- braries to reports of missing children, online services allow users to, for example, reserve airline tick- ets, buy stocks, purchase goods, and communicate with other users. In exchange for the service, users usually pay a monthly membership fee. They may also pay to connect to various databases on the service or to download information.
【单选题】● 调制解调器(MODEM)的主要功能是 （5） 。
A.
模拟信号的放大
B.
数字信号的整形
C.
模拟信号与数字信号的转换
D.
数字信号的编码
【判断题】矩形脉冲信号属于能量信号。
A.
正确
B.
错误
【单选题】ITU V90调制解调器(MODEM)______。
A.
下载速率是56kb/s，上传速率是33.6kb/s
B.
上下行速率都是56kb/s
C.
与标准X.25公用数据网连接，以56kb/s的速率交换数据
D.
时刻与ISP连接，只要开机，永远在线
【单选题】自动产生矩形脉冲信号的是( )。
A.
施密特触发电路
B.
单稳态触发器
C.
多谐振荡器
D.
T触发器
【单选题】当通过电话线连接到ISP时，因为电话线路输出信号为哪种信号，计算技术输出信号只能通过调制解调器同电话网连接
A.
数字
B.
模拟
C.
音频
D.
模拟数字
【单选题】调制解调器的功能是（ ）。
A.
模拟信号与数字信号的转换
B.
数字信号的编码
C.
模拟信号的放大
D.
数字信号整形
【单选题】调制解调器(Modern)的作用是( )。
A.
将数字脉冲信号转换成模拟信号
B.
将模拟信号转换成数字脉冲信号
C.
将数字脉冲信号与模拟信号互相转换
D.
为了上网与打电话两不误
【单选题】调制解调器的作用是
A.
计算机信号和模拟信号互相转换
B.
把计算机信号转换为模拟信号
C.
把模拟信号转换为计算机信号
D.
防止外部病毒进入计算机中
【单选题】调制解调器（Modem）的主要功能是（）。
A.
模拟信号的放大
B.
数字信号的整形
C.
模拟信号与数字信号的转换
D.
数字信号的编码
【单选题】调制解调器(modem)的主要功能是
A.
模拟信号的放大
B.
数字信号的编码
C.
模拟信号与数字信号的转换
D.
数字信号的放大
【单选题】调制解调器(Modem)的功能是。
A.
将数字信号转换成模拟信号
B.
将模拟信号转换成数字信号
C.
兼有A和B的功能
D.
使用不同频率的载波将信号变换到不同的频率范围
【单选题】周期矩形脉冲信号的周期T不变,其()不变
A.
带宽
B.
谱线间隔
C.
脉冲宽度
D.
相位
【单选题】调制解调器的英文名是( )。
A.
Modem
B.
Bridge
C.
Router
D.
Gateway