Internal Thinkpad Modem
Linux drivers for the various internal Thinkpad modems.
To identify your internal modem, it is always a good advice to start with the scanModem script from:
Grab a current version and have a look at its output.
Give the drivers for Agere Softmodems from Smartlink a try:
Although, the Smartlink driver for Agere modems (see above) is able to communicate with the modem via AT commands, it cannot dial out (contradicting reports welcome!).
If your favourite distribution does not include a hsfmodem driver (search for "hsfmodem" or "Conexant"), you can try the one from Linuxant:
(14k free as in beer, 56k+Fax license 15$, they explain this policy under: http://www.linuxant.com/store/faq.php )