将1路模拟信号编码为数字信号后，和另外7路数字信号采用同步TDM方式复用到一条通信线路上。该路模拟信号的频率变化范围为0～1kHz，每个采样值使用PCM方式编码为4位的二进制数，7路数字信号的数据传输速率均为7.2 Kbps。复用线路需要的最小信道容量是______。
A．7.2Kbps
B．58.4Kbps
C．64Kbps
D．128Kbps
参考答案：C
解析： 1路模拟信号的最大频率为1kHz，根据采样定理可知采样频率至少为2kHz，每个样值编码为4位二进制数，因此该路模拟信号编码后的数据传输率为2×4=8Kbps。
由于同步TDM方式复用的每条支路速率要相等，而7路数字信号的传输速率低于8Kbps，因此这7路数字信号均要采用脉冲填充方式，将数据传输速率提高到8Kbps。最后，该通信线路上是8路8Kbps的数字信号复用，其需要的最小信道容量为8Kbps×8=64Kbps。
| 完形填空。 | ||||
| The most well-known effect of weather 1 mood is a medical condition called Seasonal Affective Disorder (SAD for short).People who 2 from SAD get very 3 and depressed during the winter months. Actually it is 4 to do with the weather-more because during the winter, days are very 5 and people don't see so much day light(especially if they spend most of the day in a school room or of fice!). Of course, the further North of the equator you live, the 6 _ the days during winter and the more 7 you are to have symptom of SAD. When you are 8 to sunlight, your body makes lots of Vitamin D3, and because of that you make more of a substance called Serotonin ( pronounced Ser- ah - TONE- in).Serotonin is a chemical 9 in the brain and it's very 10 to your mood. We know that if you don't have enough of it then you can become depressed-antidepressant drugs like Prozac work because they 11 the amount of serotonin 12 to the brain. Scientists think that some people aren't so 13 _ at making their own serotonin, and need more sunlight than other people to do it properly. These are the people who suffer from SAD during the winter, 14 they just can't get enough sunlight ouring the short days to make all the serotonin they need to 15 happy. This is probably down to their genes. | ||||
|