mobile DTMF timing

Andreas Eversberg andreas at
Fri Jan 27 13:15:39 UTC 2012

mad wrote:
> Hi list, hi Jolly,
> I just tested the DTMF support on a real network and discovered that the timeout of 70ms for receiving the Start DTMF ACK is too short. The consequences are many repeated Start DTMF messages, never received ACKs and no tone is played. 
> Using a timer value of 170ms in mnccms.c:759 fixes this for that network.
> Unfortunately I didn't found - or overlooked - a mandatory timeout value for Ta in TS 23.014 which the MSC has to meet. 
> Is that undefined in the standard and where came the 70ms from?
> Regards,
>   Mad
hi mad,

the timeout is set after the reception of the DTMF ACK. this ensures
that the time to play the tone is at least 70ms. then the tones is
stooped, and after it has been acked, the timer is started again to wait
for the next tone. then the next tone, if any, is sent.


can you send me a log of the process when you send the dtmf tones?



More information about the baseband-devel mailing list