Warning - Having multiple types of DTMF enabled can cause issues with your system. The potential issue here is anything FS related (conference bridge, AA, etc.) can receive multiple digits. Here be dragons...

To enable detection of inband DTMF tones in sipXecs or openUC we need to make some changes to Freeswitch. To do that edit the following file:

/etc/sipxpbx/freeswitch/default_context.xml.vm

Locate the following section:

<extension name="IVR">
<condition field="destination_number" expression="^IVR${dollar}">

Add this lines bellow:

<action application="set" data="dtmf_verbose=true"/> //This allow to see the recognized tones in the Freeswitch console (/opt/freeswitch/bin/fs_cli)
<action application="spandsp_start_dtmf"/>
<action application="start_dtmf" />

Then we need to send server profiles to allow /etc/sipxpbx/freeswitch/conf/dialplan/sipX_context.xml to be generated

SipXconfig -> System -> Servers: Select server(s) check box -> Send Profiles

Sources:

http://wiki.freeswitch.org/wiki/Mod_spandsp#DTMF

http://wiki.freeswitch.org/wiki/Misc._Dialplan_Tools_start_dtmf