Minecraft wiki entry for Redstone_Torch, associated text: A redstone torch is active unless the block it is attached to is powered. Effectively, a redstone torch inverts the signal applied to its attachment block: power level 0 is changed to 15 and power levels 1 to 15 are changed to 0 (for an alternative that produces a greater range of output power levels, consider a redstone comparator in subtraction mode).