My experience with the 990's IR input has been similar to my experience with my Pace cable box's IR input - it isn't getting quite the same signal format as an IR sensor does, so a simple distribution block's output doesn't work. Instead, it appears to be using a separate communication format of some sort, which is where the interface module comes in. I got the Xantech interface module model number from Scott, and I suspect he could chase up similar module numbers for other IR distribution manufacturers.