Minecraft wiki entry for Transmission, associated text: Variation (2-wide): The two upper levels (including the dust on top of the block the repeater is facing) can be moved one block over and down, and the last block on the lower level and its dust removed, to make a 2-wide version that is shorter in height and length (but larger in volume: 2×4×3, 24 block volume). In this version, to reduce the amount of redstone used, the block of redstone can be replaced with a regular block if redstone torches are placed under both its extended and retracted position.