I used this as the repeater box. It is there you connect the receiver(s) and the transmitter(s)
I used this IR Receiver. I installed it in the front of the stage:
After everything was done, I realized I did not have a direct line of sight to that IR receiver from the back row because the chairs in the front row were blocking it! I fix that, I added this to the soffit above the screen. The cover comes off easily so I removed it and painted it black.
I used this IR Transmitter Eyebud to transmit the signal to the Windows MCE IR Receiver plugged into the HTPC. I had tried one of the IR Eyebuds I already had, but they did not work. Luckily, I had ordered a kit and had one of these to use. No idea why my other Eyebud did not work. It was old so it might just have been broken.
I ran a non-terminated CAT5e cable between each of the receivers and the repeater, then plugged an IR Transmitter eyebud into the receiver and stuck it on the HTPC IR receiver. I also plugged two mono 2.5mm (I think) mini-connector cables into the repeater. One was a male - male cable and was run to the IR Input on the AVR, the other was a male - female calbe and one to the projector. At the projector side I used another Eyebud, connected into the extension cable and stuck over the IR Input of the projector. I think I bought my kit here:
The IR Repeater box does NOT come with a power supply, so buying a kit is a great idea.