We've used a Powermid off & on with different equipment for many years and have always had to work around a problem similar to yours. When we first installed it we had Sony Trinitron monitor receivers both upstairs and downstairs. Even though they were manufactured several years apart the remote controls were interchangeable for the basic functions. Although the Powermid was only intended to operate a VCR upstairs from downstairs, the upstairs TV kept responding to the downstairs control until we turned the downstairs Powermid so that its front/sensing surface was facing the wall in a bookcase. Then when we wanted to remote control the VCR we just turned the Powermid around so it faced forward.
When we switched over to a DVD player downstairs we temporarily retired the Powermid for several years. It was put back into service again when we got a second Tivo box upstairs with an optional feed to the downstairs TV. Since both Tivo remotes were identical we were faced with the same problem again but with a new twist. Now if either Tivo got turned on unitentionally by the downstairs control while you were operating the other there was the additional possibility that you could also accidently erase a recorded program on one Tivo while erasing a program on the other. Simply reversing the Powermid wouldn't solve this problem.
Here's the final solution. First I put a switch box and pilot light in a small box attached to the bottom of the Powermid. You can't see it in the picture but it's about twice as deep as it is wide so it's quite stable.
Next I fabricated an IR blocker to cover the IR port on the downstairs Tivo. It's a piece of bent aluminum with foam rubber on the back. Here's a picture of it with the Tivo IR port exposed. It's the small black rectangle to the right bottom of the Tivo face plate.
Here's a picture of the it with the Tivo IR port covered.
Since the upstairs Tivo/TV connection is composite video and the downstairs Tivo/TV connection is S-Video the RF coax output of the upstairs Tivo is available to loop through the VCR for recording and from that via coax to the downstairs TV set which does the input switching. The S-video on the upstairs Tivo connects directly to my computer to burn DVDs. There is a composite video switch upstairs if you want to see output from the VCR on the upstairs TV, and you have to move a couple of jumpers to dub video tape to DVD on the computer.
It all seems to work very well except it mystifies my wife, which is alright with her since she has never needed to use it by herself since the feed to downstairs is mainly used to watch one of my programs that I've Tivoed upstairs.
