How to choose dtmf mode

双音多频 DTMF（Dual Tone Multi Frequency），双音多频，由高频群和低频群组成，高低频群各包含4个频率。一个高频信号和一个低频信号叠加组成一个组合信号，代表一个数字。DTMF信号有16个编码。利用DTMF信令可选择呼叫相应的对讲机。

通俗的讲，系统会将用户输入转换成dtmf信号发送出去，当dtmf出现问题时，往往一般表现为用户无法通过按键在语音菜单(IVR)中做出选择。

Usually we just need to make sure it's using correct dtmfmode in the trunk. The option is

dtmfmode= the options are

• auto
• inband
• info
• rfc2833

For example

dtmfmode=rfc2833

• For inbound/outbound, you need to make sure you configured correct dtmfmode same as your provider asked, in most case, use rfc2833
• When you are using inband, the codec need to be ulaw or alaw