The 192 comes stock with 8 analog ins, 8 analog outs and 8 digital I/O all on removable cards. However the cards cannot be interchanged. Taking the digital card out and replacing it with an analog card will cause the unit to power down with an error. The only reason that the cards are removable is for service. The unit will run without the cards inserted thereby allowing you to send in a card for service without taking your whole system down. Essentially the unit provides the same amount of I/O as an 888/24, but gives you the option of adding an additional 8 ins, 8 outs or 8 digital I/O thereby giving you.16 A ins, 8 A outs and 8 D I/O with the ADC card installed8 A ins, 16 A outs and 8 D I/O with the DAC card installed8 A ins, 8 A outs and 16 D I/O with the DIO card installedAdditionally the unit comes with 2 AES I/O, 2 SPDIF I/O and 8 Adat I/O on the unit itself which don't have SRC. When choosing digital inputs you can choose to use these or the DIO card (which does have SRC). Pro Tools 5.3 now has a patchbay like feature in the Hardware Dialog where you can choose your input sources in pairs. However when choosing a Digital input you CAN NOT mix and match sources on the DIO card. For example you can't get channels 1/2 from AES and 3/4 from analog and 5/6 from TDIF because you've already chosen to use the AES ins on your digital card.Also the ADC (both included with the unit and the optional expansion card) have both +4 ins and -10 ins which are switchable through software. Thereby allowing you to keep both patched simultaneously and choosing which the hardware will look at on a channel by channel basis (a great option for those of us with a lot of synths). The unit also comes with 2 calibration pots per channel these are also switchable though software, thereby allowing you to cal your rig for -18 and -20 (or any setting of your choice) and switching between them on a project by project basis.