There are two parts to this system. Well, more, actually.

The RX-77 part controls the components in the main downstairs system, except for the A/V receiver. This is the part of the system I am trying to integrate with the second system.

The second system runs an IR signal through a router to control either the downstairs A/V receiver or the upstairs A/V receiver, which are the same model Yamaha. Those control signals come from the RX77 via the air, going into a Xantech sensor. Again, this is the part I want to hardwire.

This second system also takes input from an RS232IR, and in addition to running the RT8 router, runs whichever Xantech volume control RAT1 is selected by the RT8, runs two CC12s, sometimes sends IR upstairs for the other volume controls up there.

Shoe, all of the stuff downstairs (except the RX77 part) is run by one 782 1 amp regulated power supply. Only IR signal and ground connect to upstairs; the upstairs has its own 782. I didn't expect CAT5 to carry enough current upstairs to run all those things.