You aren't using the system as a fax switch in the setup I outlined.
This is placing a dedicated fax line on the system, a line that only rings at the fax machine that is attached to the analog DN and just gives a line appearance on the other stations. This way it gives the customer flexibility to be able to use the fax line as a number to call out on. When the fax is using the line, it shows in use on the other stations.
Now to address what you are asking since I misunderstood your post the first time:
I think the fax DN was added around 6.0
You assign a DN to the Fax, you go to system auto attendant, turn the auto attendant on, turn the fax switch on, tell it which line to answer, the number of rings and where to route tell voice calls to. I have always found the system AA to be a pain and rarely use it.
NCSS NCTS NCTE