asterisk users - Feb 2015 - Deactivate faxdetect on IAX channel

Hi,

we have following setup:

fax machines > PSTN -> GW SIP -> Asterisk -> Peer IAX (Elastix)

Asterisk is 11.16 as well as Asterisk version of Elastix peer.

When sending incoming fax calls to the Peer IAX -which receive them 
using hylafax- we want to tell our asterisk to NOT detect fax CNG. It's 
easy on a SIP channel as faxdetect=no can be set for the peer, but how 
to do it for an IAX peer? Is this option available too?

Also, don't answering the call before sending it to the IAX peer is not 
an option.

Thanks for any hint

-- 
Daniel