Minecraft wiki entry for Zero-ticking, associated text: When a redstone signal is sent through a pulse limiter, it shortens the pulse. When the pulse is shortened enough, strange behaviors arise. If a sticky piston is powered by a 2-tick pulse, it will start extending but after two ticks, the piston will drop its block and start retracting. If a sticky piston is powered by a 1-tick pulse, the same behavior will happen, but instead of happening after 2 ticks it will only happen after one tick.