Item Unloader

The Item Unloader is a block added by Railcraft used to deposit items from a minecart with an inventory into an adjacent inventory. When the cart is empty, or meets the requirements set in the GUI the block will emit a redstone signal.

The Item Unloader will only output items to minecarts that are vertically adjacent to it. This can be changed by upgrading it to the Adv. Item Unloader.

Usage
The Item Unloader has to be placed above the track where the minecart to load will be. Locking Tracks are very useful when combined with Item Unloaders, when set to Holding or Boarding mode, because they will stop the cart when there is no redstone signal, and will force the cart to continue when there is a redstone signal.

GUI
In the GUI there is a Filters section, a Buffer section, and a few buttons. The Filters section determines which items and how many are taken from the inventory. The Buffer section is the place to put items to be unloaded. This is where the cart will dump the items.

The buttons determine the way the Unloader functions:

Top button:
 * All: Move all items from the cart.
 * Transfer: Move the exact items in the Filter.
 * Stock: Move items until the destination matches the Filter.
 * Excess: Keep the items in the Filter, and move the rest.

Bottom button:
 * Immediate: Emit redstone if no items were moved.
 * Complete: Emit redstone when the move is complete.
 * Manual: Never emit redstone.
 * Partial: Emit redstone if no items were moved and the cart is not empty.