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xDSL技术中的精华就在于能够通过现有的铜质电话线传送大量信息。这还是有可能的,因为xDSL调制解调器借助于数字信号处理技术,可向模拟线路插入并获取更多的数据。关键在于调制,在这个过程中,一个信号能修改另一个信号的属性。在数字用户线系统中,从源Modem中发出的调制信号改变了高频载波信号,形成一个复合波,称为调制波。由于这种高频载波信号可以调制,就能比普通铜导线传输的距离更远,也能承载更大容量的调制后的数字信号。到目的地址后,由目的Modem进行解调。
The essence of xDSL technology is the ability to send a large amount of information over an existing copper phone line. This is possible because the xDSL modem inserts digital data and gets more data with the aid of digital signal processing. The key is modulation, in the process, a signal can modify the properties of another signal. In the digital subscriber line system, the modulated signal sent from the source modem changes the high-frequency carrier signal to form a complex wave called a modulated wave. Since this high-frequency carrier signal can be modulated, it can travel farther than normal copper conductors and can carry a larger volume of modulated digital signals. To the destination address, the purpose of Modem demodulation.