I wanted to buy a transformer for the speed regulator, so based on this image, I bought a transformer with 12V DC output. It works.
However, discussing this with a fellow AFOL, he pointed out that his (original from LEGO) transformer has a 10V AC output, as seen in this image.
So... which one is correct? Or they both work? Or there are different versions of the speed regulator with different input requirements?