This block will detect things on the block in front of it. If there is an item or block in front of it that matches the chosen block/item assigned to it, it will emit a redstone signal. The GUI will contain a button that when pressed will invert this process making the detector detect all blocks and items that are NOT specified. In addition to that, the player can also enter block/item IDs with metadata value for precise block detection for blocks and items that can't be obtained. Detectors will ignore conveyor belt blocks, and will detect both items on the ground and items moving along a conveyor belt.