Minecraft wiki entry for Pulse, associated text: The Slime BUD made possible by Minecraft 1.8 works great as an instant inverted dual-edge detector. Simply put a block of obsidian, a hopper, afurnace, etc. right next to the slime block, and run redstone from its top to your output, and put a piece of redstone dust on the same plane as the piston, with one block space between. That's your input.