Minecraft wiki entry for Redstone_Dust, associated text: The "power level" of redstone dust can vary from 0 to 15. Most power components power-up adjacent redstone dust to power level 15, but a few (daylight sensors, trapped chests, and weighted pressure plates) may create a lower power level. Redstone repeaters output power level 15 (when turned on), but redstone comparators may output a lower power level.