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。

DTMF (dual tone multi frequency) is the signal to the phone company that you generate when you press an ordinary telephone's touch keys. Without correct DTMF, a IVR could not understand what's customer input.

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