Stacked Observers

I need to know if any of nine blocks, in a 3x3 wall, are updated. Right now I just put a 3x3 wall of observers. I only need one output signal saying "Yes, one of the 9 blocks were updated". e.g., piece of my wall was broken.

So right now, directly behind the wall, I put a 3x3 wall of observers. But I can only pull signals from the bottom three observers. The stacked observers GIVE a signal, but I have no way to retrieve that signal.

1 Answer

This should do the trick. The top and bottom rows are powering blocks, which in turn, power the redstone line.