US Patent 9235740 Automatic drawer state detection

An inventory system can include radio frequency identification (RFID) tags and RFID tuners that can be brought into interacting proximity with one another to provide input or other information about the location or other condition of movable elements within the inventory system. For example, a closed or at least partially open state of a drawer can be determined based on signals from an RFID tag when the RFID tag and a corresponding RFID tuner are mounted on opposing faces of the drawer and a compartment that receives the drawer.