The first task you will need to do is to identify whether your modem's chipset is HCF or HSF. Unfortunately the traditional way of doing this (by using /proc/pci, lspci or KDE's control center) won't work for us here due to errors in the pci.ids file which can cause a misidentification of the modem. There are three main ways which you can use to identify your modem's chipset:
If you've got your modem working under Windows then you can identify your chipset by downloading and running Conexant's ListModem Application. When you run it, the program will give the information we want under "MODEM TYPE".
If you've opened your computer up chances are that the modem's chipset will have either the letters "HSF" or "HCF" printed on it.
You can identify your type of modem from it's device ID and vendor ID, the easiest way get this information is from the command lspci -n (or less /proc/pci on older Linux distributions) this command tells you all of the Vendor IDs and Devices IDs for all of the PCI cards in your machine. You will be able to identify your modems' IDs as it will have a vendor ID of either 14F1 (Conexant) or 127A (Rockwell). Ignore any information that the lspci command tells you about your modem being a HSF or HCF as it could be wrong.
The information is often presented in the form VVVV:DDDD where VVVV is the vendor ID and DDDD is the device ID, for instance if it listed 127a:2005 it would mean the that the Vendor ID is 127a and device ID is 2005.
If your modem is a HCF modem it will have one of the following Device IDs:
1033 / 1034 / 1035 / 1036 / 10b3 / 10b4 / 10b5 / 10b6 / 1003 / 1004 / 1005 / 1023 / 1024 / 1025 / 1f10 / 1f11 / 1f14 / 1f15
If your modem is a SmartHCF modem it will have one of the following Device IDs:
1052 / 1053 / 1054 / 1055 / 1056 / 1057 / 1058 / 1059 / 1063 / 1064 / 1065 / 1066
If your modem is a HSF modem it will have one of the following Device IDs:
2013 / 2014 / 2015 / 2016 / 2003 / 2004 / 2005 / 2006 / 2f10 / 2f12 / 2f00
If your modem is a SmartHSF modem it will have one of the following Device IDs:
2043 / 2044 / 2045 / 2046 / 2053 / 2054 / 2055 / 2056