Having owned two of them, I seem to remember the D2 having a digital signal capability, like CGA or something. I got familiar with the manual after the original 1084S went all whiny and blew a flyback transformer and I seem to remember something about that.
i think you are thinking of the 1902/1902a, one had the digital/analog switch
all 1084's work with commodore 128 digital rgb tho
