[Freeswitch-users] DTMF Problem with T-Mobile carrier

Phil Kim phil.kim at valiant.com
Mon Oct 3 18:33:13 MSD 2011

Hello everybody,


I really need some help here!


I'm trying to use FS for making both inbound and outbound calls through

Everything works perfectly except one particular situation with DTMF

In case of inbound calling (I'm calling FS), everything works fine. Call
connects and I can send DTMF to FS and FS recognized those 100% (Testing
with softphone from my desktop, SIP phone in the office, and all
wireless carriers)

However, I am having trouble with outbound calling. I have set it up to
where FS makes an outbound call to certain number and once the call is
answered, we start playing some custom IVR. 

Here, it works fine with softphone from my desktop, SIP phones in the
office, AT&T, and Verizon. But for some reason FS will not recognize the
DTMF coming from T-Mobile cell phones.

Anyone has any idea? Below are my current setting from external.xml
which was recommended by Broadvox.


<param name="codec-prefs" value="PCMU,G729"/>

            <param name="dtmf-type" value="rfc2833"/>

            <param name="auto-rtp-bugs" value="clear"/>

            <param name="pass-rfc2833" value="true"/>      

            <param name="inbound-late-negotiation" value="true"/>


            <param name="sip-trace" value="no"/>

            <param name="sip-capture" value="no"/>        

            <param name="rfc2833-pt" value="101"/>

            <param name="sip-port" value="$${external_sip_port}"/>

            <param name="dialplan" value="XML"/>

            <param name="context" value="public"/>

            <param name="dtmf-duration" value="1000"/>

            <param name="inbound-codec-prefs"

            <param name="outbound-codec-prefs"

            <param name="hold-music" value="$${hold_music}"/>

            <param name="rtp-timer-name" value="soft"/>




Best regards,


Phil Kim


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