Minecraft wiki entry for Redstone_Repeater, associated text: A repeater set to a delay of two to four redstone ticks increases the length of any shorter on-pulse to match the length of the repeater's delay, and suppress any shorter off-pulse. For example, a repeater set to a 4-tick delay changes a 1-tick, 2-tick, or 3-tick on-pulse into a 4-tick on-pulse, and does not allow through any off-pulse shorter than 4 ticks.