该模型利用事件通告机制来传送双音多频信号，通过SUBSCRIBE和NOTIFY两个消息来实现交换机对SIP终端的完全控制。
This model offers SIP Specific Event Notification to transmit DTMF, and USES SUBSCRIBE and NOTIFY to realize the control to IP phone.
该系统用MI-TEL公司的DTMF收发器MT8880芯片作为电话双音多频信号的解码核心，用AT89C5 1单片机作主控器，电路简单灵活。
The system uses MT8880 (made by MITEL company) as the decoding chip of DTMF telephone and chip AT89C51 as the microcontroller, so, the circuit is simple and adaptive.
在传输网络中，音频适配器采用双音多频芯片MT8880实现数据格式的转换功能，对讲机则完成对转换后的音频信号收发功能；
In the transmission network, the audio adapter adopts MT8880 to transform the data format and the wireless interphone is to transmit and receive the audio signal.
在传输网络中，音频适配器采用双音多频芯片MT8880实现数据格式的转换功能，对讲机则完成对转换后的音频信号收发功能；
In the transmission network, the audio adapter adopts MT8880 to transform the data format and the wireless interphone is to transmit and receive the audio signal.
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