QUESTION FAX: Select trunk for each modem?

[l4cky]

Number 1 (3 channels)
Number 2 (different provider) (only 1 channel)

I would like to use number 1 mostly for incoming and outgoing voice calls.
I would like to use number 2 mostly for incoming and outgoing FAX.

My incredible fax installations give me 4 modems: ttyIAX0,ttyIAX1,ttyIAX2,ttyIAX3.

How do we setup the modem to use by default number 2 trunk, and if busy, to use number 1 trunk for outgoing faxes?

(I was thinking maybe linked ttyIAX0 to number 2 trunk --> but no way to do this and then get the ttyIAX0 to be set as default for incoming/outgoing faxes --> also don't know how to do it)

Assuming if it is possible, what can we do not to screw up the order for outgoing calls as number 1 trunk set as preferred over numbre 2 trunk?

thanks