A detector, system including a detector and method for sensing motion within a detection region. The detector has a detection element and a focusing element aiming received energy corresponding to a presence within the detection region toward the detection element. The focusing element has a plurality of sections in which each of the plurality of sections establishes a corresponding detection zone within the detection region. The plurality of sections are arranged to allow a motion vector to be determined for an object passing through the detection region. The system includes a detector that generates pulses each time presence in a detector zone is detected as well as a central alarm panel. The central alarm panel receives the pulses and has processor that evaluates the timing between electrical pulses to determine the motion vector.