[X1] How Do They Do It?

I had to replace one of my Xi3 boxes this past weekend. When I connected and powered it up, I was expecting to have to re-pair the old remote with it... but, it automagically paired itself with the remote! Then, yesterday, just for grins I went to set up the XR15 remote that came with the new Xi3 with our XG1 DVR, it did the same thing... and, paired to the TV too! I was expecting to have to find the right code to control the TV, but that was automagic too. Didn't like the XR15 so much, but that's a different post here. How do they do that? Does the box know the TV make/model via the HDMI handshake? Cheers!