You might want to look at this page, guys, which does a pretty good job of explaining the problem:
Essentially, what I think NeverSurrenderer is identifying is the host signal processor type of "modem", which, as you'll see from reading the article, actually consists of little more than a telephone-cable-shaped port and a few resistors to protect against powersurges ;).
HSP's can usually be recognised at a glance - Connexant actually puts 'HSP' in the name of their HSP modems, I believe.
The real point to note, is that these things need software to allow your main CPU do the work traditionally done by the modem's own hardware. A lot of these modems rely on the software provided by Windows to do this, of course (a file called windows!, which forms part of the actual Windows subsystem, if I recall correctly), but this does not preculde other software for other opperating systems being written for them instead. Indeed, many of Rockwell's Connexant modems have Linux drivers written for them by Linuxant, who also provide documentation to help you understand things like the AT command set used by modems (imagine actually being able to understand what your modem and you ISP's gateway are talking about, when you read 'Klog'! Now, that is the _epitome_ of sad 8-). Their website is here:
They have a commandline tool for telling you whether your modem is one they provide for, and RPMs of the actual "drivers".
Sometimes you will find Linux software to control and run your software for sale at a small price from the people who developed it. This, of course, runs dead against the GNU/Linux philosophy, and explains why most Linux distributers don't ship with these drivers on their disks. The software _will_ get your modem working, however, if you really want it to.
However, we must realise that, when dealing with pieces of hardware that retail, as new, for less than fifteen UK pounds sterling (convert to your own local currency, here), the financial and, indeed, the /philosophical/ urge to make software available for them isn't that great. The old lie is that Linux is used for servers, and indeed, Google and Amazon both use Linux, but I don't think they use many modems... Anyone who uses desktop Linux will tell you that it is one of life's major experiences in visual gorgeousness, against which Windows looks like a drab totallitarian world of grey paving slabs that have "OK" written on them (even when it's really NOT "OK"). Indeed a fully working KDE desktop with 3D accelaration, transparent hover menus, drop shadows, multimedia previews, and 1280x1024 resolution, goes a long way towards beating the wizz-bang chaotics of Mas OS X's "agua" desktop. However, we are in a minority, in recognising this, at present.
On a final note, SuSE Linux boast about a 50% hit-rate in supporting internal 'Winmodems', but you'll still need to buy any drivers for modems whose control software isn't available for free, and some just aren't going to be available unless you write them yourselves. When one considers how much longer any of us are actually stil going to be using conventional modems for anything, I'm sure you'll realise that some things aren't worth the effort.