It also has an automated output to the side the arrow points and must be provided with small amounts of Energy Units (EU) to function. By using a Screwdriver on its output, the Chest Buffer can be programmed to output only Stacks of a certain size (e.g., Always sending 8 Items into a Furnace to avoid wasting Coal).
Clicking on the Lightning button in its GUI will cause the Chest Buffer to transfer its energy to the machine it is exporting to. Clicking on the Circuit symbol will cause the Buffer to send out a redstone signal when the Buffer is full. The RS Torch button will invert the signal.
Even through its automated output does not work without energy, other machines can still pull items from the Chest Buffer. The stack size control will still work.