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1·Many traditional single simplex communication devices now can act as a duplex system under the help of voice activated module, which is actual voice activity detector.

很多单工的通讯设备可以通过语音检测技术的应用实现收发状态的自动转换而以比较小的代价达到双工设备的功能。

2·The master control chip uses AT89C51, the communication mode adopts DTMF signal with strong anti-interference and high reliability, and simplex frequency modulation.

主控芯片采用AT89C51单片机，通信方式采用抗干扰能力强、可靠性高的DTMF信号和单工调频的无线通信方式。

3·Simplex: Data communication in one direction only. Contrast to Full duplex , Half duplex.

单向：数据只作一个方向的传送。有别于全变向，半变向。