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Looking at this video about the new pistons in Minecraft 1.7, he has arranged 3 horizontal-pushing pistons in a stack vertically and is using an alternating pattern of redstone torches to activate them together.

  D'||=|
  'D||=|
__D'||=|
*D for dirt; ' for redstone torches; ||=| for pistons; and _ for redstone wire

What minecraft circuit wizardry is in play here that makes all the pistons activate together when the input is on? Furthermore, could the pattern be extended upwards indefinitely like this?

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2 Answers 2

up vote 18 down vote accepted

The circuitry behind this is fairly simple. It relies on the principle that the default state of a Redstone Torch is on, and that when power is applied to the block that it is mounted on, it will turn off. When no power is applied to the bottom block in the circuit, the bottom and top Redstone Torches are on, and the middle is off, because the bottom one is powering the block the middle one is attached to.

The bottom piston is on because the bottom Redstone Torch is powering it. The middle piston is also on, because the bottom Redstone Torch is powering the cobblestone directly above it, also powering the piston adjacent. The top piston is on because the top Redstone Torch is powering it.

enter image description here

When a current is applied to the bottom block of cobblestone, the bottom Redstone Torch is turned off, because it is mounted on the cobblestone. This makes the bottom piston retract. Because no power is being applied to the middle cobblestone block, the middle piston turns off, and the middle Redstone Torch also turns on (because power isn't being applied to it anymore). This, in turn, turns off the top Redstone Torch (because power is being applied to the cobblestone block it is mounted on), turning the top piston off.

enter image description here

And yes, this design can be repeated upwards infinitely (but there will be a noticeable delay between the topmost and bottommost pistons, as it takes time for each Redstone Torch to change states).

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I'll just delete my answer and upvote yours. –  Shazang Jun 30 '11 at 22:42
    
Thank you very much for the upvote, but you didn't have to delete your answer - it's always good to have multiple answers per question. –  Kevin Y Jun 30 '11 at 22:44
    
@Shazang The middle piston is also on, because the bottom Redstone Torch is powering the cobblestone directly above it, also powering the piston adjacent. This is primarily what what mystifying me, thank you! @KevinY Your answer was a good one, which I almost accepted, but I decided to hold out in case someone knew the actual mechanics as to why it worked. Thank you as well. –  Keeblebrox Jun 30 '11 at 22:50
    
@Keeblebrox I think you mixed up your @notifications there. ;) –  Kevin Y Jul 1 '11 at 3:33
1  
@KevinY I haven't the slightest idea what you're talking about, Shazang. –  Keeblebrox Jul 1 '11 at 7:05

That's a redstone inverter. A nice, compact one. I've no idea if they can be extended any higher, but they can be reversed and stacked horizontally forever.

Take a look at this example using the same method:

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