<include>

<extension name="dialExt1002">

<condition field="destination_number" expression="^(1234)$">

<action application="set" data="drop_dtmf=true"/>

<action application="export" data="drop_dtmf=true"/>

                        <!-- Add a bind_meta_app just to make sure that the rfc2833 is still being picked up -->

<action application="bind_meta_app" data="4 b s execute_extension::att_xfer XML features"/>

<action application="set" data="ignore_early_media=true" />

<action application="set" data="ringback=${uk-ring}"/>

<action application="set" data="call_timeout=30"/>

<action application="bridge" data="user/1002"/>

</condition>

</extension>

</include>

I am trying to prevent the DTMF tones from being heard by the b-leg (in this case user/1002). 

This works fine if the extension is called by a registered softphone (the user_context is set to public). The digits are pressed and no beeps or tones are heard by the other side.

If this extension is dialed by a landline/mobile number, when a digit is pressed there is a slight "bleeding" of the DTMF.  Enough to distinguish between different digits, though probably not enough to determin the digit pressed.

I have tried several things such as stop_dtmf in the dialplan, setting the dtmf-duration to 0 (not quite sure what this param does but tried it anyway :) ) in the sip profile but nothing seems to prevent it.

Could it be our provider? They have confirmed that they use out-of -band rfc2883. But without the drop_dtmf being set in the dialplan the full tone is heard. Could they be sending inband and out-of-band?

Could anyone suggest any tests I could run or any log files I could look at please?