There are different drivers available. To find out what kind of software modem you are using, go to [http://www.linmodems.org linmodems.org], read the page, and download the scanModem tool (which will only recognize PCI and USB modems, not ISA modems). Copy it to your desktop in your Ubuntu machine, then open a command line and enter:

•  $ cd ~/Desktop
   $ gunzip scanModem.gz
   $ chmod +x scanModem
   $ ./scanModem

Gunzip will 'unzip' the file, chmod will mark it as executable, and ./scanModem will run it. If it tells you to do something as root by issuing su - root, instead just enter the commands it wants following a "sudo", e.g. $ sudo modprobe snd-intel8x0m. scanModem will scan your modem and tell you what it is and how to configure it. It will not configure it for you. But after running, you will see a number of new folders, including a 'Modem' folder. Read read1st.txt and modemdata.txt in there, and see if you modem was recognized. This is admittedly not a straight-forward read and might need some more reading around on above mentioned page to find out which drivers your modem needs. Then scan through the following sections to find out about the easiest way to install that driver under Ubuntu.

Note: For many of the following drivers, you will need to enable the universe/multiverse repositories. See AddingRepositoriesHowto. This requires you to have working network connection. You can also search for packages to download in another system and transfer to your Ubuntu installation at http://packages.ubuntu.com/ . Be careful with the dependencies... Check out this forum post for another way to get packages using the LiveCD on another system with network connection and a CD burner: http://www.ubuntuforums.org/showpost.php?p=893732&postcount=6

Now that you know what modem you have, you now want to check out which of the following modem instructions apply to you. This list is from [https://help.ubuntu.com/community/DialupModemHowto the main wiki page].

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3. [:DialupModemHowto/AlsaModem:Modems supported by ALSA drivers (snd_atiixp_modem, snd_via82xx_modem, snd_intel8x0m)]

4. [:DialupModemHowto/Smartlink:Modems supported by the Smartlink driver]

5. [:DialupModemHowto/Lucent:Modems supported by the Lucent driver]

6. [:DialupModemHowto/Intel537EP:Modems supported by the Intel537EP driver]

7. [:DialupModemHowto/Intel536EP:Modems supported by the Intel536EP driver]

8. [:DialupModemHowto/Conexant:Modems supported by the Conexant drivers]

9. [:DialupModemHowto/PcTel:PCTel Modems]

(...)