[Asterisk-Users] Asterisk missing DTMF tones from some cell phones

[Steve Underwood]

Hi Bryce,

Bryce Nesbitt (mailing list account) wrote:

> While most cell phones are fine, some cell phones don't seem to 
> produce DTMF digits that Asterisk/Zapata will detect.  One of our 
> salespeople has an AT&T model that never gets any digits through.
>
> Is there a known solution?
>
> I understand, of course, that with cell phones the DTMF tones are 
> actually created at the base, and that pressing the key longer usually 
> does not result in longer tones.
>
> I have seen 
> http://lists.digium.com/pipermail/asterisk-users/2004-February/037319.html 
>
>
>             -Bryce
>
> PS: I'm actually using the http://www.mipl.org browser, which does
>    zap_getdtmf(zap,1,NULL,0,0,0,ZAP_HOOKEXIT), etc.

As you have found, the cellphone does not generate the DTMF, so the 
model is irrelevant. However, which network it is on might be. The DTMF, 
which is actually generated by the cellular infrastructure, consists of 
very long bursts of tones on most networks. Much longer than the usual 
50ms to 100ms of DTMF most land line phones generate. If should be 
generated with high quality, though, so detection should be reliable.

Regards,
Steve