Minecraft wiki entry for Randomizers, associated text: This randomizer utilizes the fact that droppers dispense items in random order. It will output a random signal strength of 1 or 3 whenever a signal is provided. To create it, place a dropper, hopper, and comparator as shown. Then put items of varying stack size into the dropper, e.g. a sword and a piece of dirt. When you power the dropper, it will put an item into the hopper, turning on the comparator. Since the items take up different amounts of space, the power level will vary. It may seem as if adding items that stack to sixteen will allow an output of two, but unfortunately unless the hopper is weighted with items beforehand, items that stack to 16 only result a level of one.