Tutorials/Item sorter

Introduction
Most item sorters (made possible in 13w01a) work using hoppers. More specifically, a hopper with all five slots occupied by, for example, redstone, will only be able to collect redstone, because there is nowhere for any other items to go.

Connecting the hopper to a comparator will allow the sorter to measure the contents of the hopper. All five slots MUST remain occupied by the material you are sorting for, otherwise other items will be able to pass through. The easiest way to ensure this is to measure for a 2-strength signal from the comparator, which corresponds to 21 items inside - 17 inside the leftmost slot and 1 each in the other four slots (hoppers lose items in the leftmost slot first).

Components
There are two components to an item sorter: the item channel and the sorting component(s). Here is an analogy to clarify this: the item channel is like a river, and the sorting components can be imagined as nets that only catch certain items. The river ends in a dump (the junk chest).

The item channel is simply a path that items travel through. It can be a horizontal chain of hoppers, or a water channel. Hoppers underneath the hopper chain or water channel act as the "net" and will extract items.

The sorting components are composed of hoppers. To enable deposition and extraction to be independently toggled, two hoppers must be used: one on top of the other, and the top one pointing sideways. The top hopper should be connected to the comparator, which will power the bottom hopper (which takes items out of the top hopper)