I recently helped someone install Ubuntu 8.04 on a couple of IBM(now Lenovo) Thinkpad T41, and we couldn't get the modem to work... at first.

This is what comes up on $ lspci | grep Modem

00:1f.6 Modem: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) AC'97 Modem Controller (rev 01)

In one of the laptops, we did: $ sudo modprobe snd_intel8x0m (mind the “m” at the end, there is a snd_intel8x0) and the modem came up on System --> Administration --> Hardware Drivers

In the other laptop if didn't work like this... so we had to investigate a little more. The modem in the T41 is a soft-modem or winmodem by Smartlink. There is a Linux driver available for this modems, the one we used is actually in the Ubuntu repositories, it's called sl-modem-daemon, the version at the time of this article was 2.9.10.

$ sudo apt-get sl-modem-daemon

This driver installs successfully and allowed my friend to connect to his dial-up ISP. Some of the more advanced features like voice modem and faxing are not supported in Linux yet though.

The driver creates a device at /dev/pts/0 and a symbolic link to it /dev/ttySL0. To dial we tried gnome-ppp and it works like a charm, but although this software is very good, it doesn't let you create more than one connection. So we used pppconfig (it comes installed by default in Ubuntu 8.04). Pppconfig lets you create, delete or edit connections, it asks you some questions about it:

$ sudo pppconfig

Create a connection

Provider name: this is the name of the connection, don't use spaces or special characters, keep it simple.

DNS: The best option is dynamic DNS but if your provider has different settings select the appropriated one.

Authentication protocol: PAP, Chat, CHAP. There is no best answer here, it depends on what your ISP supports. PAP is what MS Windows uses. Chat is also widely supported, CHAP is the same as PAP but encrypted. We selected Chat.

Login prompt: Leave it to the default.

Password prompt: leave it to the default.

User name and password.

Modem speed: Leave it to the default.

Method for dialing: Tone is for touch-up phones and pulses for the old phones with a dial.
Number to dial: Provided by your ISP.

Port where your modem is: The auto detect should work, if it doesn't don't worry, write it manually to:
/dev/ttySL0 (mind the uppercase/lowercase)

Now pppconfig is going to put all the settings together for you to review, but we are not done yet, select 'Advanced Options', find the option 'Add user'. Here write your username, not for the ISP, but the one you use to log-in to Ubuntu. This is going to give you permissions to use the connect and disconnect commands.
Select Previous, and then Finished.

Now to connect you will use: $ pon followed by the Provider name. e.g.: $ pon att

if pon gives you any problems or doesn't dial, try it with sudo, $ sudo pon Provider name and if that doesn't do it, check the device, it may not be /dev/ttySL0, but this is unlikely, also check if you wrote it exactly as here, with uppercase and lowercase characters. If still it doesn't work do this:

open two consoles, in one execute: $ sudo tail -f /var/log/messages
                                    in the other execute '$ pon Provider name' or '$ sudo pon Provider name'

in the console with tail you are going to see messages writen by pon, copy them and paste them here in the comments or in the forums so we can help you out.

To disconnect use '$ poff Provider name' or $ sudo poff Provider name

If you have any questions about this article use the comments.