I don't know much about the technology, but in math 2+2 always equals 4. No exceptions. I would think the same would hold true for IR signals. If you can learn one signal, then you should be able to learn any IR signal since the signals all work on the same principal. However, I have a couple remotes with keys that refuse to be learned by my universal remote. I've tried different times of day, different lighting, different distances, yet no success. What is it about IR signals that make learning a hit and miss proposition? Thanks.

IR is a frequency band, just like visible light (as seen in the different colors). Some remotes may transmit frequencies that are too high or low to be detected by your universal remote.

What are the OEM remotes that won't shoot? Some manufacturers use a 2-part code that require Universal Remote software that has the ability to learn both parts of the code and put them together.