asterisk users - Oct 2007 - Two DTMF tones on keypress with Handsfree cell

Hello, I am using Asterisk SVN, a cellular phone, and chan_mobile to
run a small home PBX with two analog telephones connected to a Linksys
ATA using SIP. It works great (except for some Bluetooth adapter bugs
that I am still trying to beat...seems the misaligned audio detection
still needs work), but I have encountered an interesting issue.

If I am using an automated system that accepts input using the
telephone keypad DTMF tones, pressing those keys on my analog
telephone emits the tone once, and then about a half-second to a
second later the cell phone does the same thing, because the ATA
adapter transmitted the DTMF press digitally as well. The only system
I've tried to interact with so far also accepted voice input, so I
didn't have a chance to test further and see if it was my fault
(pressing a wrong key) or the dual-tone problem that confused the
system on the other end. Is there some way to suppress DTMF tones at
some point in the call routing? Or disable the phone sending DTMF
tones during the actual call?

Thanks in advance for any ideas or input.

-- 
~Andrew