Its a CF card with a digital input (mini optical or coax). I've been using one since last fall with an iPaq 3835 and 5GB pcmcia drive. Seems pretty solid for 16bit, but I've had major problems recording 24bit with Live2496 and Wichita software. I did receive an update for the Live2496 recording software a few weeks ago that is said to improve 24bit recording, but I haven't had a chance to test it.