I've seen videos that explain how to make redstone double doors, but none of them really explain why redstone double doors work that way, just that they do.
Is there an explanation for their behaviour?
closed as too localized by OrigamiRobot, GnomeSlice, Wipqozn♦, Frank, badp♦ Aug 13 '12 at 20:05
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Doors have two states, "open" and "closed". When you place two doors next to each other, the game automatically moves the 2nd door 90* and swaps the state (if it didn't, you'd just have two identical doors next to each other).
In manual use, the state isn't important, but as soon as you connect the door to redstone, it becomes very important: doors without charge go to the "closed" state, and doors with charge go to the "open" state. Because the doors are not next to each other in their "closed" state, you get the weird behavior you've observed.