The Item Detector is a block from Redpower Machines.
When put between two or more Pneumatic Tubes, it will emit a redstone signal (from the side with a red square, the wire must connect to the edge closest to the item output face) once the contents of the tubes meet one of three conditions. The conditions can be configured in the right-click GUI and are as follows:
- A single item goes through. (If it detects a stack of items, it will emit one redstone signal for each item in that stack before stopping)
- A stack of any size passes through.
- An item is backstuffed into it.