[Asterisk-Dev] HELP: DTMF signals screwed up by asterisk

[Asterisk Developer]

hello,

I tried to use an analog emergency-call device. that device is a one-button 
device that calls an emergency service like 911, it's for older people or 
people with disabilities. however, the device dials out to a remote server to 
login and gather some information. when the device dials the number, the 
server answers with a 2000hz tone and a DTMF sequence. that DTMF sequence is 
however totally screwed up by asterisk. each dtmf sequence is 80ms long, but 
asterisk cuts out 40ms from the sequence. it looks like:

 *******00000000000000*******
 0-----20-----40-----60----80---->
 ms                           

* = DTMF signal 
0 = no DTMF signal

call direction SIP<->ZAP<->E1 (TE410P). I have a WAV file and a PNG image of 
the waveform. see http://www.jass.at/asterisk/

do we have a chance to turn off DTMF detection within zaptel/chan_zap?

Thanks in advance
Alf Scherer