A new problem (was: Re: Waking up the computer via telephone)

This is now working as I said in an earlier posting

However, there appears to be a rather idiotic problem now in as much as the computer actually falls asleep again within a few seconds after the ring when no fax as been received (as none was sent to it). This happens even when I am logged in via SSH.

Is there a way to make Mac OS X not fall asleep when a user is using the computer?