Minecraft wiki entry for Pulse, associated text: A pulse length differentiator has two outputs and one input. Long pulses go through one output, while short pulses go to the other. It also keeps the tick length of the signals, which is why all the repeaters are set to one tick (i.e., a 1-tick signal will stay a 1-tick signal). This is useful in a telegraph machine, in order to split up dashes and dots.