| 摘要 |
A traffic light control system comprises a passive infra-red presence detection system for detecting the presence of a target emitting infra-red radiation, which comprises a pyro-electric detector including an array of pyro-electric sensor elements. The pyro-electric detector is arranged to generate a signal representative of movement of the target within a detection zone of the detector. By priding a signal processing unit which operates to analyse pulses present in the signal, the said presence detection system is provided with a means whereby it can not only detect movement of the target within the detection zone but also whether that target has moved into and stopped within the detection zone.
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