I assume it is the serial one?
The usb equivilent is powered by the USB port so I guess it is safe to say it has to be close to 5v.
If you have to buy a power adaptor for it I'd just get a new pci modem instead. It will probably be better.
<A HREF="http://www.folken.net/myrig.htm" target="_new">My precious...</A>