Patent ID: 7448545

Claim:
Apparatus for monitoring items passing through an entry/exit opening in a delimited space, comprising: radio-frequency transmission means ( 2 ) adapted to communicate with a plurality of transponders associated with said items to detect the presence of the transponders in proximity of the opening, each transponder being adapted to transmit a specific identifier code, at least a pair of optoelectronic sensors ( 3 , 4 ) arranged in series at said opening, each sensor ( 3 , 4 ) being adapted to transmit a first signal identifying a condition of clear sensor, in which said sensor ( 3 , 4 ) detects the opening as being clear, and a second signal identifying a condition of locked-on, i.e., engaged sensor, in which said sensor ( 3 , 4 ) detects an item passing through said opening, characterized in that control means ( 5 ) are provided to continuously store and/or update the time-based detection events of the transponders and the time-based variation events of the signal transmitted by the sensors ( 3 , 4 ), said control means ( 5 ) being adapted to compare said time-based variation events of the signal transmitted by the sensors ( 3 , 4 ) to determine an opening passing-through time interval (T), and to compare the time-based detection events of the transponders with said passing-through time interval (T) to determine the transponders that have passed through the opening completely.