This card was one of the first upgrades available for the CDTV (The other being the CD1300 & CD1301 Genlocks), It fits in the CDTV's expansion slot at the rear of the CDTV, next to the Video slot and gives the CDTV both an internal 50 pin and external 25 pin SCSI connector,
The card supported the SCSI 1 standard and was capable of up to 1 Meg a second and sold for only £50 (Which is cheap for any Amiga SCSI card).
The SCSI card was also included in a complete harddrive kit with the CDTV`s own black external 80 Megabyte harddrive for £256. If you think 80MB is small then dont, The OS took up 0.8MB of that space and Amiga software only normally occupied one 0.8MB floppy disk so it would take 100 programs to fill the drive... But still it isnt a patch on the 640MB the CDTV can hold on a CD-Rom.
There is only one version of this card and it will work in all CDTV's regardless of country and only one version was made by Commodore.
Lots of other companies made similer cards but often cost the same as the official Commodore interface, Sometimes they even cost more, All are listed on the Upgrades page.

What is SCSI?
SCSI is a way of connecting devices like harddrives and CD-Roms to computers, very much like IDE does but with three big differences:
It does not require the CPU: Unlike IDE (at the time) the SCSI interface will copy data directly to memory which is the key to the CDXL video format. You can connect many types of upgrades to it like harddrives, CD-Roms, scanners, tape drives to name a few. You can connect more: Each SCSI card can have seven (.......) devices attached where as IDE can only have two (..) at best.

SCSI is also very good at backwards compatiability, What I mean is you can plug a modern SCSI 2 drive onto an SCSI 1 interface and it will work, Even the new 68 & 80 pin drives can work with an SCSI 1 interface if you buy an adapter (Which just dumps the extra signals), As long as SCSI is alive the CDTV will be able to use modern SCSI drives.