Darrellx
Fax/CO lines are a resource that is very under-utilized at most locations, at least in my world, so I always add it as a CO line to the Magix system and assign it to a button on some phones and set the button for no ring. I instruct the customer to use it to call out only, and show them what it looks like when the fax is in use.
I use a spare analog extension in the Magix, set (auto line sel)to grab the CO Fax line (801->?)first.
Mike