Asterisk and Aethra compatibility?

Hi All,

I have running Asterisk 1.4.4

I have two video endpoints from Aethra registered as SIP devices.

My problem:
I cannot seem to get DTMF for IVR to work when the Aethra unit calls Asterisk.

It seems the DTMF tone length is not long enough for the IVR to detect successfully and direct call.

Has anyone out there successfully married an Asterisk box and an Aethra endpoint?

What settings for dtmfmode used in Asterisk?