I have a Xfinity X1 system with a Pace Xi5 Set Top Box. The remote control uses RF by default. However, you can reset the remote control to use IR by using following steps:
Press and hold the "Setup" button, which is located at the bottom left side of the Xfinity remote control. Hold the button until the red light turns to a green light.
Then enter 987 on the Xfinity remote. It should blink green twice, and from there-on, it will use IR instead of RF.
You can verify that it's using IR by covering the front of the XFinity remote control, and verify that the channels don't change. Uncover it, and the remote buttons should work again.
Once the Xfinity remote is in IR mode, you can teach your Harmony remote contrrol.
I'm not sure why, but on my setup the Xfinity remote control automatically reverts back to RF after a while.
But even after it reverts to RF, the Harmony remote control still works using the learned IR codes.
I tested this out on a Harmony 880 remote.
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