Digital data can also be represented by (71)si
问题详情
Digital data can also be represented by (71)signals by use ofa modem. The modem converts a series of binary voltage (72) into an analog signal by encoding the digital data ontoa carrier frequency. The resulting signal occupies a certam spectrum of (73) centered about the carTier and may be propagated acrossa medium suitable for that carrier. The most common modems represent digital data in the voice(74)and hence allow those datato be propagated over ordinary voice-grade (75 )lines At the other end of the line, another modem demodulates the signal to recover the original data
(71)
A.analog
B.digital
C.Modem
D.electric 请帮忙给出正确答案和分析,谢谢!
参考答案
正确答案:A
数字数据也可以通过调制解调器用模拟信号来表示。调制解调器把数字数据编码为一种载波频率,从而可以把二进制电压序列转换为模拟信号。产生的信号占用了以某一频率为中心的载波频带,可以通过适合于该载波的介质进行传播。大多数通用的调制解调器表示话音频带的数字数据,因而允许这些数据在通常的话音级电话线路上传播。在线路的另一端,另外一个调制解调器对信号进行解调并恢复原来的数据。