I haven't used the outputs of the RF extender to connect into the multi-in, but I have used a flasher output from a Xantech kit (291-kit) and plugged it straight into the multi-in on the receiver and it worked fine. The codes are the same as the normal "main room" codes. The only difference is whether the receiver picks it up on it's front IR receiver or through that back port.

I had to use two different IR kits/receivers in order to separate the main room stuff from the commands coming in from around the house....not sure on how you're planning on using the RF extender but if you're also using it for the main room controls then you need to make sure that you'll be able to send commands ONLY to the back port.

Hope that made sense......let us know how you hook it up.

Nick