There are actually two variants of the Diamond SupraMAX USB Modem. Look on the label on the underside - there it should say something like 2820 or 2920.
www.linmodems.org links to
this page (it has a
huge database of modems). I believe the 2820 is supposed to be supported, but has not been reported as such, whereas the other one is not supported at all. It is enfuriating - I bought the non-supported one ages ago.
If it turns out that you have the unsupported one aswell, then I would suggest you sell it and get yourself a serial modem.
