Minecraft wiki entry for Zero-ticking, associated text: A regular redstone repeater can't be used to refresh the signal of a 0-tick pulse as they would extend the pulse to a length of 2 ticks. So one must use a 0-tick repeater. A 0-tick repeater works by receiving an input as a 0-tick pulse, which will 0-tick a redstone block that is inside of the 0-tick repeater. And right after that, the redstone block is 0-ticked back to it's original position. This can be used to repeat 0-tick signals, but one must note that they add block event delay.