Thank you for advices.
In my aplication the speed it is not the main request (V22bis will be enough).
So I could use modem on ISA bus. The problem is that are very hard to find now in 2001.
We well Know the PC designers decision : ISA out from new motherboards !.
I would like to use the same circuit after two years from now on.
I'm sure the V90 is the last for ordinary telephone lines.

The prices for a PCI modem are around 15-25$.
As you already know, include everything (modem, DAA, country approved).
Try to make your own from spare parts. You will not succeed to fit in 15$.
Just think about the prices for 600 ohms transformer in single quantity.

The prices for external modem are more higher than internal.
So even if seems more comfortable to interface it is not my favorite solution.

I understand that interfacing with PCI modem it will not be peace of cake.
I don't request assembly code. Just some good links.
I know the meaning of signals on PCI and the behavior of this interface.
But I like to know more how comunication with PCI modem works.

Thank you for patience.