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一、前言现在,通信种类繁多,有话音、数据、图象通信等等。因此往往有这样的要求:例如使用一条通信线路同时传输话音和数据二种信息。一般认为,同时传送模拟信号和数字信号的方法有频分多路制(FDM)和时分多路制(TDM)等。但是,如果采用频分多路制,则频带就要加宽,为了频率分配,需要调制解调设备。若采用时分多路制,需要将模拟信号变成数字信号的设备,以及在收发之间要加帧同步的设备。从频带有效利用及设备的成本来看,用以
First, the preface Now, a wide range of communication, voice, data, image communications and so on. Therefore, there is often such a requirement: for example, using one communication line to transmit both voice and data information at the same time. It is generally believed that the methods of simultaneously transmitting analog signals and digital signals are Frequency Division Multiplexing (FDM) and Time Division Multiplexing (TDM). However, if frequency-division multiplexing is used, the frequency band should be widened, and a modem device is needed for frequency allocation. If using time division multiplexing, the need for analog signals into digital signal equipment, as well as send and receive between frames to be added synchronization equipment. Effective use of the band and the cost of equipment point of view, to