According to the AOpen manuals, fm56-svv has the Conexant CX11252-11 chipset. This is the best thing I could find:
https://www.linuxant.com/drivers/.
I couldn't find anything about fm56-dx.
If you have the modems in a computer:
/sbin/lspci -v
will help identify the chipsets of the modems (if they're PCI).
Lyle