PDH传输系统数字段的定义是什么?

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问题:

PDH传输系统数字段的定义是什么?

考点:传输线路维护人员考试光缆通信光缆通信题库
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下列词语中涉及的光现象与“小孔成像”形成原因相同的是(   )

A.凿壁偷光

B.海市蜃楼

C.猴子捞月

D.杯弓蛇影

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如图,某广场一灯柱AB被一钢缆CD固定,CD与地面成40°夹角,且CB=5米,

求钢缆CD的长度;(精确到0.1米)

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下图所示的调制方式是(48),若载波频率为 2400HZ,则码元速率为(49)

48()

A.FSK

B.2DPSK

C.ASK

D.QAM

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(C)

It looks like a mobile phone(手机), but the service is much cheaper. It acts like a mobile phone, but only in your own city. Beyond the city walls, it’s useless.

“Little Smart”, also called “xiaolingtong”, has always been compared to mobile phones. But actually, it is more like one of those cordless phones(无绳电话) used around the home. The only difference is that this one reaches much further than from the bathroom to the living room. It can travel across an entire city.

Cheap costs are the main reason for the success of Little Smart. It costs 25 yuan a month for the line and about 0.1 yuan per minute to use. A mobile phone, on the other hand, can cost four or five times as much. What’s more, unlike mobile phones, there’s no fee(费) for incoming calls. So these low charges have attracted many users.

But, Little Smart is not really that smart. Users often complain about its bad voice quality. And there are not as many stations to pick up its signals(信号)as there are for mobiles. “I couldn’t receive a phone call if I was on a bus,” said Li Ping, a user in Hangzhou. “It worked fine when I stood still, but there were breaks in signal when I was moving.”

Scientists are trying to make Little Smart more user friendly. Messaging and Internet access(接入) have been added to the service. And the latest Little Smart handset even has color screen.

31. Why is Little Smart popular in China? ___________

A. It looks like a mobile phone.        B. The service is much cheaper.

C. There is no fee for incoming calls.   D. All of the above.

32. How is the charge of Little Smart? ______________

A. About 10 fen per minute to use.    

B. It costs four or five times more than a mobile phone.

C. It only costs 25 yuan each month.  

D. There’s no fee for calls.

33. Why are users not satisfied with Little Smart? ___________

A. They can’t hear each other clearly out of the city.

B. There are so few stations for Little Smart to pick up its signals.

C.    When you use it, you must stand up.      

D. The charges are low.

34. The underlined word “handset” in the last paragraph means “_________”.

A. the hand bag      B. telephone      C. service        D. mobile phone

35. What can we infer from the passage? ________________.

A. It’s wrong to say that Little Smart is smart.  

B. Scientist are trying to make Little Smart smaller.

C. Little Smart will be better than today.   

D. People will change Little Smart into a mobile phone.

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某公司2002年成立,2003年1月开始营业,在此期间发生登记注册费4000元,差旅费1000元,其他费用2500元。建造工程的借款利息为5000元,购买设备的外币折算损失为4000元,该公司的开办费为( )元。

A.7500

B.16500

C.9000

D.12500

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