I have the manual for the Niles as well as the Xantech.
Everything is already wired using Cat 5. As I said, the installation in the house is complete, by the previous owner. However, I have a different receiver (Denon 3808-CI), so I was trying to figure out what cable I needed to go from the Xantech to the Denon.
Thanks to these messages I think I finally found the right input on the Denon -- it is suspiciously labeled Remote Control input -- which in hindsight is pretty obvious -- but there are a MIGHTY lot of connectors on the back of this baby, and I only found it by looking at the schematic in the users manual. I probably would never have found it by just looking at the back of the box.
So, now I will get the right cable and attempt to get the programming set. Thanks for the tip that Niles has good customer service. I'll try the manual first, but if I can't succeed after several attempts I will give them a call.