Depends on total # of lines. Ie. As the total number goes up, the
statistical chance that someone will drop offline and a line will be
available at any instance in time during peak load intervals will
increase. As an example, with only 10 lines even 5:1 is too many
users/port. With over a couple hundred lines 10:1 is a good target
ratio. Of course, you are going to have to talk about the number of
lines that are actually available for dial-in. If you are silly enough
to offer unlimited, flat-rate, unmetered or whatever the current
euphemism is, you will have to count on "X" number of lines taken up
by the hangers-on, the abusers. You subtract that number of lines from
your total modem pool BEFORE you figure customer to modem ratios.