I did some research into European elevator codes and got the impression that depending on country there was either DO/DC or a single Door Hold button - but it s

I did some research into European elevator codes and got the impression that depending on country there was either DO/DC or a single Door Hold button - but it seems like the labeling on DH might be identical to DO on some elevators which creates sort of a philosophical question as to if they're really different things. Still, you can find elevators with DO, DH, and DC it seems, and in that case I have no idea what the difference is between DO and DH. It's kind of hard to cover this stuff in Europe as the degree of variation from country to country is pretty high, so pretty much any rule you state won't apply in some major city that people will bring up. Perhaps I should have been more explicit, but in general I hope the discussion of ADA and the ASME code makes it clear that I'm talking about the US. Actually the ASME code mostly applies directly to Canada as well as a separate but harmonized code.