Minecraft wiki entry for Pulse, associated text: Wall blocks (cobblestone wall etc.) instantly transmit signal arbitrary distance down by turning themselves and all wall block below from smooth wall segment to a pillar segment if certain blocks are placed on them or attached from a side. To form a smooth segment, a wall needs two other wall blocks or other blocks wall can attach to, adjacent to it from two opposite sides. If they are other wall blocks though, it doesn't matter if they are smooth or pillars - so the solution is 1-tileable, but requires uninterrupted columns of full blocks (or wall) on far ends. Probably the most practical way to toggle a wall between these states is a redstone-controlled trapdoor. The readout through an observer is only possible from below though, as the wall connects to an observer from a side.