阿郎笔试题

贝尔的题
First Section:Common to all
partI
1.Why is non-linear quantization method adopted in A/D transformation?
A) To reduce quantization errors
B) Because most of signals are non-linear
C) Both A and B
D) Neither A or B
 
2. About digital signal:
A) It is discrete in tim domain
B) It has a limited number of values
C) Both A and B
D) Neither A or B
 
3 In order to restore the digital original signal, the sampling frequency
F has the following constrains:
A) F<=2Fs
B) F>=2Fs
C) F>Fs
D) F<FS
 
4.the procedure of digitalization has the following seqence:
A) Sampling,quantization,coding
B) Sampling,coding,quatization
C) Quatization,coding,sampling
D) coding,quantization,sampling
 
5 the purpose of coding is
A) To improve SNR provided the bit rate is constant
B) To minimise bit rate proivided the constant SNR is given
C) Both A and B
D) Neither A or B
 
6 At present time is PCM communication ,the sampling freqency to
speech signals is  
 
A) 4k
B) 8k
c) 16k
d) 20k
 
7 In HDLC frame ,synchronous code is
A) 01111110
B) 01110010
C) 11110000
D) 10101010
 
8 A multiframe of 30/32 channel PCM is made up of 16 consecutive frames.
the time length of such a multiframe is
A) 2ms
B) 1ms
C) 250us
D) 125us
 
9 the network synchronous mode adoped in the digital commucation network in  
china
is
A) Quasistable synchronous mode
B) Master-Slave mode
C) Master-Slave mode combined with quasistable synchronous mode
D) Mutual synchronous mode
 
10 About the advantage of using digital switch and tansmission instead of an
alogue ons,
with one is wrong
A) Economy
B) Reliability
C) Save of bandwith
D) Improved transmission quality
E) Integration of speech and data transmission
 
Part II
Make a judgement True or False
1. Parity code can both check and correct errors
2. In 30/32 channel PCM frame struct, every frame transmits frame
synchronous code in TS0(first time slot)  
3. The analogue subscriber speech signals are transmitted and
received via 2 bi-directional wires ,but the digital ones via 4
one-directional wires
4.A distributed swicth system has higer reliability and security than
a central control
5.cmm is capacity maturity model
 
Part III
1.请写出中断执行一般流程
2 下面是一些基本的数字电路问题，简要回答
1）什么是setup和holdup 时间
2）什么是竞争和冒险现象，怎么判断，如何消除
3） 什么是同步逻辑和异步逻辑
4） 你知道哪些常用的逻辑电平，TTL和CMOS电平可以直接互连么
5）什么是“线与”逻辑，要实现它，再硬件特性上又什么具体要求
6。。。。。
7）已给出基地址/cs0=F000H和16位地址线A[15:0],译出三个外设片选，其
地址为/cs1=F100H /cs2=F200H /cs3=F300H /表示低有效
3。请分别画出osi的参考模型和TCP/IP的参考模型
4。请列举通信行业中常用的不同体系构架的cpu种类，并举例说明
附加题
请谈谈你对SDH的理解
1）SDH相对PDH的特性差异
2）SDH中不同的低速等级数据速率的映射关系（请以STM-1为例）
3）请画出STM-1的帧结构图
 
阿尔卡特笔试题
部用C语言完成：  
　　1．自己定义数据结构，写出程序：在一个单向链表中，往I位置插入一个节点。  
 
　　2．自己定义数据结构，写出程序：二叉树的前序遍历。  
 
　　3．不允许使用系统时间，写出一个随机数生成函数。  
 
 
　　这次是连环游戏，每一题的答案将在下一题中用到。  
 
　　1、{first 10-digit prime found in consecutive digits e}.com.  
 
　　e中出现的连续的第一个10个数字组成的质数。  
 
　　2、7427466391.com  
 
　　Congratulations,Youve made it to level 2. Go to www.Linux.org and enter  
 
Bobsyouruncle as the login and the answer to this equation as the password.  
 
　　f(1)=7182818284  
 
　　f(2)=8182845904  
 
　　f(3)=8747135266  
 
　　f(4)=7427466391  
 
　　f(5)=__________  
 
　　update：提示：f(1)到f(4)是e中连续的10个数字满足总和等于49的前4个，f(5)当然  
 
是让你搜索第5个咯，编个小程序吧。  
 
　　答案：5966290435  
 
　　3、www.Linux.org  
 
　　4、www.google.com/labjobs/  
 
　　via:  
 
　　Google recruits eggheads with mystery billboard  
 
　　Mysterious Billboard May Be Google Recruitment Ad  
 
　　Myserious billboard  
 
　　Google is behind mystery geek trap  
 
　　写一句俳句来描述搜索流量季节性预测的可能方法。  
 
　　用三种颜色为一个二十面体涂颜色，每面都要覆盖，你能够用多少种不同的涂法？你  
 
将选择哪三种颜色？