Several months ago, I received a Roco model of the BLS 486 locomotive ("Die Alpinisten: / "Gli Alpinisti" lettering), which I had ordered months before that.
While installing a decoder this month, I discovered, almost by accident, that the F1 function turns on the second set of headlights. (The primary headlights have to be turned on with the F0 light control, and the second headlights change with direction of travel.)
This was not mentioned in the documentation that came with the model. Of course, I bought the model as an analog model, without a decoder -- though, like all other current Roco models, the locomotive had a decoder socket.
As Roco also offers several other versions of the Swiss 486, I assume this feature also applies to those models, though I do not recall any mention of it in Roco catalogs.
Have any of you found other undocumented features on models, once you installed a decoder?
The experience with the BLS model will certainly prompt me to be sure to try out the F1 and F2 functions on other models when I install decoders.