To make a VoIP infrastructure using ISDN lines.
Using ISDN PCI slot or do the job for a separate gateway PATTON?
PCI Cards are working very good and they are cheaper . Im using PCI cards except I need to implement fail-over scenarios .
I have very good experience with Patton gateways.
Both solutions are OK. You just have to decide if you want your server to do TDM-VoIP conversion. I personally prefer that a dedicated gateway takes care of that.