As far as the dsl modem goes...
Wow, amazed this is supported, it took some googling, but it seems that Itex became Pulsar and sold the same chipset... so, these drivers may or may not work:
http://adsl4linux.no-ip.org/cgi-bin/engine.cgi
If you're using a newer distro like RH9, Mandy 9.x, SuSe 8.1/2, Slack 9, but not any Debian aside from Unstable, then you should get the gcc 3.xx version.
As far as the regular old winmodem:
http://www.linuxquestions.org/questions/answers/34
Is a pretty good place to start on tracking down drivers, like the Itex, which chipset is what counts most.
Cheers,
Finegan