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【单选题】
ADSL(非对称数字环路)业务是宽带接入技术中的一种，ADSL是采用 (23) 调制通过双绞线向用户提供宽带业务、交互式数据业务和普通电话服务的接入技术，其上行速率为0kb/s～1Mb/s，下行速率可达1Mb/s～ (24) ，有效传输距离为3～5km。ADSL接入互联网的两种方式是 (25) 。
Cable Modem又叫线缆调制解调器，它可以连接用户家中的PC机和 (26) 网络。Cable Modem的最高上行速率可达 (27) ，下行速率则更高，彻底解决了由于声音/图像传输而引起的阻塞。
A.
ATM
B.
PSTN
C.
HFC
D.
FRN
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【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 interface (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】计算机常通过传统的调制解调器或综合业务数字网络技术接入因特网，数据传输速率都不超过128KB/s。目前已有多种更高数据传输速率的宽带接入方式，如仍采用电话线的 (16) 、采用有线电视双向改造后的电缆的 (17) ，以及光纤到大楼再通过局域网到户的 (18) 等方式。
A.
HDTV
B.
HFC
C.
W-ISDN
D.
N-ISDN
【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 interface (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】计算机常通过传统的调制解调器或综合业务数字网络技术接入因特网，数据传输速率都不超过128KB/s。目前已有多种更高数据传输速率的宽带接入方式，如仍采用电话线的 (16) 、采用有线电视双向改造后的电缆的 (17) ，以及光纤到大楼再通过局域网到户的 (18) 等方式。
A.
HDTV
B.
HFC
C.
W-ISDN
D.
N-ISDN
【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
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