The realization of the DTMF circuit using discrete components was presented in this paper. 给出了双音多频发送电路的分立元件实现方法。
Instead of the integrated chips for five-subdivisions, the discrete elements are used in the experiment to reduce the cost. 该文的实验通过用分立元件代替集成五细分芯片,从而降低了实验成本。