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【单选题】

People talked about a promising idea: using the electrical wiring already in the house to move data from room to room.One early application, the X10 system for controlling lights and appliances, didn't always work well.The technology was certainly not ready to be used to bring web pages to computers anywhere in the house.
Along came the wireless network.For 50, you could get the Internet sprayed across the house and never be confined by a cord to the wall.It was slow in those early days, very unreliable, and open to interruption if you couldn't bother with setting up the encoded passwords.
But it caught on.According to estimates made by Parks Associates, a market research firm based in Dallas, about 12.5 million homes now have wireless networks; another 10 million homes, mostly newer ones, have Ethernet(以太网).
Cheap and prevalent is a hard combination to beat.However, technology companies continued to work on the idea.A version for power lines called HomePlug came out in 2002, and while it hardly affected sales of wireless network equipment, it sold enough that major companies like Intel, Cisco, Sony, Sharp and Comcast created the HomePlug Alliance to push for next-generation products, with the first to come out later this year.
Some companies are not waiting.Panasonic, Netgear, Marantz are already offering products that will move data through home electrical lines faster than routers(刻纹机) using the current Wi-Fi standard for wireless networking.
Panasonic started selling its HD-PLC Ethernet adapters for power lines last month.One adapter is attached to a router with a short Ethernet cable and plugged into a nearby wall socket.The second device is plugged into a socket elsewhere in the house.When a computer is linked to it with an Ethernet cable, data is transmitted through the home's electrical wiring at speeds of up to 190 megabits(兆位) a second.
Netgear will be selling a similar system next month for about $300.It moves data at a slightly faster rate.
Marantz says its ZR6001SP receiver will send music to special speakers in another room over power lines.The system includes both devices.The music listener controls the receiver and the CD players connected to it from a control pad on the speakers.
These products seem hopeless candidates.Who would like to pay two or three times expensive than wireless network? The answer lies in simplicity.'It's why most people need us', Robert said, noting the complexity of installing a wireless network is evident by the fact that return rates on wireless networking devices drop to nearly zero.The three products' makers said that people who cannot get whole-house coverage with a wireless system or those plagued by dead zones might find it appealing.
The promising idea mentioned in the first paragraph ______.

A.
has mature technology to support it
B.
has a stable early application—the X10 system
C.
is to transmit data by power lines within the house
D.
fostered products which affected wireless network
题目标签:刻纹以太网
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【单选题】快速以太网的主要产品是(61)。

A.
HUB和100Mbit/s双绞线
B.
HUB和适配器
C.
光纤和100Mbit/s双绞线
D.
适配器和100Mbit/s双绞线

【单选题】10Base-T以太网中,以下说法不对的是:

A.
10指的是传输速率为10Mbps
B.
T指的是以太网
C.
Base指的是基带传输
D.
10Base-T 是以太网的一种配置

【单选题】以太网交换器具有()

A.
既能隔离网段又能连接网段的功能
B.
隔离网段的功能
C.
连接网段的功能又能路由的功能
D.
连接网段的功能

【多选题】工业以太网设备的重要部分有 ( ) 。

A.
工业以太网集线器
B.
工业以太网非管理型交换机
C.
工业以太网管理型交换机
D.
工业以太网管理型冗余交换机

【单选题】以太网的最大帧长度是()。

A.
1500Bytes
B.
1482Bytes
C.
1518Bytes
D.
没有限制

【多选题】以太网的特点包括( )

A.
接入、安装方便
B.
覆盖的范围广
C.
网络稳定
D.
技术成熟,成本低