Hi!
I'm assuming that you can't have an analog modem connected
while the DSL modem is still connected, it's one or the other?
No. They're two different kinds of modems. One is for DSL, the other
is a conventional analog modem.
Any analog modem should do what you need, and it sounds like you don't
have one right now (or that the one you have is not properly
recognized/installed). Some modems are better than others, but an
inexpensive 56K/V92 modem available at any computer parts store should
be fine.
Most analog modems sold today require the computer to do all the work
of shuffling data through the modem. This used to be quite finicky and
older computers could not do it well. Today's computers do not have
the same problems (as they have much more processing power) and the
software that makes these work has gotten better.
Still, if your computer is older, or if you simply want one, true
hardware-based modems can be found. They tend to cost more but contain
all the hardware needed to be a modem without requiring your computer
to do all the work of data transfer. These are typically external
modems.
You can get internal modems that plug into a slot inside your computer
or external ones that could plug into a USB or serial port on the
outside of your computer. Internal modems take all the power and
everything they need from the slot you install them in.
External modems require external power and a cable to plug them into
the computer. Their main advantage is portability--if you need to take
it to another computer, it's easy to do.
William