The Emperor Dalek is just a really big Dalek that doesn't look much like the other Daleks. His voice sounds exactly like what was shown in the preview for next week. Davros is
not the Emperor Dalek, don't think that he is. In one episode, he was disguised as the Emperor Dalek only to keep his presence a mystery until the end of the episode. The Emperor is not really
suspended by cables, he's just stuck and the cables connect him to, as I would imagine, life support and some kind of computer system. By the way, I don't know that much about the Emperor Dalek because the only episode to feature him, "The Evil of the Daleks," was destroyed by the BBC.
Here are some more photos of the Emperor Dalek, attached.