双音多频是一种在话音信道用音调来表示数字的方法，它可以用来在模拟话音信道传输信令，因此在通信中有广泛的应用。
Provide is a voice channel and tone to represent Numbers method, which can be used to transmit analog voice, so in communication has been widely used.
双音多频(DTMF)是一种在话音信道用音调来表示数字的方法，它可以用来在模拟话音信道传输信令，因此在通信中有广泛的应用。
Provide (DTMF) is a voice channel and tone to represent Numbers method, which can be used to transmit analog voice, so in communication has been widely used.
设计出了二次调制系统：采用连续可变斜率增量调制（ CV SD）实现模拟话音信号与数字编码的转换，采用二进制相对相移键控（2 DPSK）作为数字调制方式。
A twice modulation is designed:, CVSD was adopted to realize conversion between analog and digital voice signals, 2DPSK was used as the digital modulation mode.
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