The Retriever can be considered as a wireless Filter. It will retrieve items from the nearest inventory connected to the tube network on the input side, the same way as a Filter would retrieve it from an inventory directly connected to it. This can enable the same tubes to act as a delivery system as well as a reception mechanism, even in tight spaces.
The input can be easily identified as it is orange. The output can easily be identified as it is grey.
How To Operate It
A Retriever must be powered with Blutricity and also requires a redstone pulse; it will not function otherwise.
Small Space Management
The retriever is usually used in areas where space is an issue. It allows you to remove items from inventories without using a filter next to an object, so it can be used to make a central retrieval hub. This allows you to control everything from a central location.
Using As A Personal Inventory Finder
To retrieve an object from an inventory simply place it in the GUI. This could be easily used as a way to find necessary items from a very large inventory room. This could be done by having a kind of one of each item chest, which could be placed into the GUI to find an item in your chest systems. This would mean something could easily be found if a player is too lazy to actually put something away in the right chest.
In AnyStack Sequential, the slider moves from slot to slot horizontally from top left to bottom right, until it can satisfy an item or number of items (e.g. a stack). It then proceeds back to the top left hand corner.
In AnyItem mode, the retriever will attempt to satisfy any item in the grid by moving through each slot in turn.
As it is Redpower2 logic for Pneumatic Tubes to send an item to the nearest possible output; it can be advised to have all retrievers to have an item to collect, even if you place an item that is likely to be impossible to enter the current tubing system; e.g. a block of obsidian in a farm. This stops the wrong items leaving through an empty, yet powered retriever.