How can I activate / configure the 56K modem Connexant 20585 of my Lenovo Thinkpad X201

Following the info page of CX20585 - ThinkWiki the modem is part of the intel chipset and is supported since long ago.
I have my audio running flawlessly as 5 Series/3400 Series Chip-set High Definition Audio, but no modem is there. I tried to install the modem as a IHC5 (modem) but this fails with an interrupt problem. Which makes me think that this driver can be installed only once the other has been uninstalled. Is this correct? Or do I have to define such a modem as a second sound card?
The specifications of the thinkpad X201 I join them here: Detailed specifications - ThinkPad X201, X201s
Thanks for illuminating me.

The modem is a completely different piece of hardware than the sound card. The first thing I’d do, is check in the BIOS whether it’s enabled. One of my ASUSes had a modem + RJ45 connector, but the option to turn the thing on was available only after a BIOS update.
Is the modem visible in Yast - System - Hardware info? If so, what does it say about loaded drivers?
Plus, what would you use the modem for? These days many of us don’t use 56K modem connections.

Sometimes very rarely you find yourself in a setting where a 56k modem is the only thing that works. It is a laptop.
But another valuable piece is the fax function. I would like to be able, to send a fax when necessary.

It is not an urgent thing. I think these things should be done when one has (too) much time on his hands. So then, when urgency is there, everything will be prepared and available. As the modem should be well supported it is also a technical interest to see whether I can do it and how it is done.

It does not seem to be there, so I will follow your advice to look into the BIOS, maybe I have to switch it on explicitly. (Thanks, I did not think about that).