[Asterisk-Users] Sending DTMF out-of-band over IAX2

[Mark Johnston]

I am planning to deploy a fairly standard PSTN-dodging setup, like this:

T1 - * - IAX2 - * - T1

In other words, two Asterisk boxes with T100Ps, interconnected with IAX2,
used for bridging calls from one PSTN endpoint to the other.  What makes
this interesting is that on the receiving end, there is an IVR that isn't
under my control, so DTMF has to pass between the boxes.

I'd like to use GSM to save bandwidth, but I know DTMF won't survive
anything less than alaw.  Is there a way for the sending Asterisk to pick
up DTMF from the inbound Zaptel channel, send it out-of-band across the
IAX2 link, and have the receiving Asterisk synthesize the DTMF on the
outbound Zaptel?  I know all of the components (DTMF decoding, out-of-band
transmission, and synthesizing) are there in Asterisk, but I don't know
how to make them work together to accomplish my goal.

Thanks,
Mark