The line I am going to use is a live line that doubles as a fax line. If I am in when the phone rings, I answer it (I took off the answering machine).
Besides using it for the fax, I use it for certain suppliers to call me. For the most part I only get 1 call on it every 2-3 weeks but several faxes a week.
When it rings, it just doesnt bother everyone else in the house like the other number (I have 2 extensions for that line and not 8 for my regular phone).