Minecraft wiki entry for Hopper, associated text: When a hopper receives a redstone signal (and is considered to be "activated"), all three functions stop. To avoid confusion over the terms "activated" and "deactivated", powered hoppers are often described as being locked and unpowered hoppers described as being unlocked. Hoppers can be powered by soft powered blocks, meaning a redstone dust trail pointing into a block touching the hopper locks it just as effectively as a redstone block or any other power component touching the hopper. When the hopper is unlocked during a redstone tick, it does not push or pull/collect during the same tick, but has a delay of 1 redstone tick instead.