The arrangement can be used to monitor a space and if used with a second arrangement, whose directional mirrors are arranged to provide new sensing curtains adjacent {HEAD ~ the curtains} of the first detector, {TAIL ~ the arrangement} can determine the direction of movement of the object passing through the space 
The arrangement can be used to monitor a space and if used with a second arrangement , whose directional mirrors are arranged to provide new sensing curtains adjacent { HEAD ~ the curtains } of the first detector , { TAIL ~ the arrangement } can determine the direction of movement of the object passing through the space
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