Don't mix 'em up, folks. The ICN card is a "direct" ISDN card, like the
Teles, Creatix and whatsoever. There is no UART on them, and you need a
special device driver like isdn4linux or U-ISDN to run them. No modem
functionality in hardware. Potentially no IRQ required. Runs transparent
HDLC, syncPPP, X.75 etc. whatever the device driver and user level software
allows.
The others are ISDN terminal adapters, external or internal. Look,
feel, taste and behave like modems. Internal TA's have UARTs & need
IRQs. External UARTs are connected to a free serial port but normally
you cannot use their full data rate when using both channels because a
serial ports normally only can do 115,200 bps. Neither requires special
drivers. In many cases you cannot run transparent HDLC over them but
you need async PPP or X.75. There are exceptions like the Zyxel 2864DI
which will run SLIP over the RS232 line and sync PPP over ISDN if you
like. U.S. TA's often have the NT built in.
http://www.muc.de/~hm/linux/linux-isdn.html. Needs some updates...