Minecraft wiki entry for Clock, associated text: A fader pulser is useful for making small clocks with periods less than 15 seconds (for longer periods, hopper clocks can be smaller), but they are difficult to adjust to a precise period. They use a fader circuit (aka "fader loop" – a comparator loop where the signal strength declines with every pass through the loop because it travels through at least one length of two or more redstone dust), renewed by a redstone torch every time it fades out.