On mine the tty/0 (or com 1), has the mouse. The modem is on tty/1, 2, or 3
I found a good cheap modem by Stratitec model IC56A, that goes right on. I was having problems with modems that would not connect also. I got this one at Walmart for $23.85. I could not find it listed at Pricewatch.
Its instructions has the URL,
http://www.stratitce.com/ic56a
It is PCI and V92, runs on Kernel 2.4 or later.