Bob's Minecraft Tutorial, linked by Billy ONeal, is a useful resource, but I'll try to put the basics into words.
How is it possible for the torches to
work as both input and output to a
circuit?
Is there a practical difference between torches on the ground and torches on the wall?
Depending on where the torch is placed, neighboring blocks will be inputs or outputs, but each neighboring block is EITHER an input or an output - no blocks are both.
- A torch on the ground (in other words, on top of a block) outputs power in the 4 cardinal directions, and also outputs power to any block in the air above it.
- That torch will only accept input from the level below it, so input wires must run straight into the block the torch is sitting on.
To summarize, torches on the ground output to their level and input from the level below.
- A torch on a wall (in other words, on the side of a block) outputs power in only 3 directions (it doesn't output back into the block it's mounted on).
- That torch will accept input from the top of the block it's mounted to, and from the other 3 sides of the block it's mounted to.
In summary, torches on a wall output onto the ground and take input through the wall block.
What if two torches are both acting as output to the same redstone-wire?
What if one torch is outputting positive/on/true to a redstone-wire but another is outputting negative/off/false to the same wire?
This has been answered elsewhere, but: If any power source hooked up to that wire is on, the wire will be lit up.
How do I read the diagrams on the minecraftwiki page?
Again, I'll try to break down the basics:
- White squares are just air, nothing special
- Yellow squares are blocks
- Dark yellow squares are blocks a level below (that is, they're an abbreviation for "white on this level, yellow below")
- Grey squares are blocks on the current level with other items a level below
White and yellow squares can then have these items on them:
- Red lines are wires
- Red circles are redstone torches (which may be attached to the side of a block or sitting on one)
- Grey circles are levers
- Small dark grey rectangles are pushbuttons
- Large grey inset squares are pressure plates
So, for example:
- a red line on a yellow background is a wire on a block
- a grey circle on a yellow background is a lever on a block
- a red line on a grey background is a block over a wire
- a grey circle on a grey background is a block over a lever
Within the MCRedstoneSim program you can change levels and see the wiring and such on each level of the circuit, but these extended types of blocks exist so that the whole circuit can be communicated with one set of symbols and no need to show diagrams per level.
Sorry, I misread, as this time set bug annoyed me a long time on SMP server.
Known bugs on Minecraft Wiki #Redstone Torches
This is a know bug, all you can do is restarting your game. It happens sometimes on random blocks, and it will never work again on that block until you restart.
It happens both on single and multiplayer, we hope it will be fixed on 1.8
Best Answer
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.
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.
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).