There's 3 types of stock I/Os in a Vewlix. JVS, Fast, and USB. What you have is the USB I/O. It's for use with a TTX4, I think it might also "just work" with a regular Windows PC. It does have a unique harness (G1) that is different from what the JVS and Fast IOs use (G).
For JVS you want one...