Since the Flyer is dual-stream, it requires 2 SCSI busses for video, one for each stream; however, for cuts-only video, one can get by with only 1 bus (but I don't know anyone who does it this way). Audio is recorded along with the video signal on the same SCSI bus, but an extra SCSI bus is provided for recording other audio - narration, music, etc. Since there are 3 different SCSI busses, all can be used simultaneously. So it's possible to have 2 video streams and at least 4 stereo audio tracks playing at the same time (but that's kinda tricky to do!). Also, since it's SCSI2, you can hook up to 7 drives to each bus. There's no limit to the drive size (not that I know of) or file size. So if you get one of those 74 gig drives you can record a clip 74 gigs in size and play it back! And if you had enough money, you could hook 21 drives to the Flyer. Pretty impressive, I'd say!
Video input to the Flyer is provided via the connecting cable from the Toaster, as is video output. Audio in/output is through the audio jacks on the right side of this card.The serial ports are provided to control serial-capable VTRs and the like, among other things. I don't know a lot about this as I don't use it.
This particular card was bought used and had some sort of plastic coating on the mount bracket, and I'm not sure who put it on there or why. I have another card that was bought brand new and doesn't have the plastic coating, so don't be alarmed if your card doesn't have the coating.