An array of spaced parallel linear radiation beams are projected across a passage in sequentially spaced regions. Detectors sense when the beams are interrupted by one or more persons moving in the passage in either of two opposite directions. The beams are interrupted at different times in a sequence...http://www.google.fr/patents/US5519784?utm_source=gb-gplus-shareBrevet US5519784 - Apparatus for classifying movement of objects along a passage by type and direction employing time domain patterns
Apparatus for classifying movement of objects along a passage by type and ...
