John,
I would like to be able to tell you the answer to your question, but I
can't without understanding a few more details about the problem and the
Mac environment.
Certainly two programs can use the same modem on the same serial port, but
they cannot do so simultaneously. You would have to load one program and
run it or load the other program and run it. If you attempt to multitask
the same port with two programs, there will be chaos. This is really not a
modem hardware issue, but rather a software and system issue.
In a networked environment, you can establish a 'communications server'
which can allow various people to share a single modem, but only ONE person
can use the modem and its attached telephone line at a time.
– Paul 02/25 07:03