Minecraft wiki entry for Miscellaneous, associated text: Variations: If the dropper is powered indirectly (for example, by quasiconnecitvity or an adjacent powered block), the hopper is not be deactivated and immediately pushes the item back into the dropper. This turns the circuit into a monostable rising edge detector with a 3.5-tick output pulse (still with a random power level of 1 or 3).