asterisk users - Aug 2005 - ATA186 can not generate dtmf

Hello:

 I have problems sending dtmf signal to an ATA186 my configuration is:

 ATA186 --> asterisk --> ATA186 --> FXS to FXO Converter --> PSTN

 The ATA186 are set to send dtmf RFC2833, but it seems that the ATA186 can't
generate dtmf so I can dial to a PSTN number.
 Is there a setting that can fix my problem, inband dtmf does not work 
because I'm using G729 codec

 Thanks

Erick