Minecraft wiki entry for Redstone_mechanics, associated text: Redstone dust transmits power to adjacent redstone dust and blocks, but its strength decreases by 1 for each block the redstone power travels. Redstone dust can thus transmit power up to 15 blocks before needing to be maintained with a redstone comparator or re-strengthened with a repeater. Power level only fades with the dust-to-dust transmission, not between dust and a device or block.