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Nocturnal graffiti artists beware. Traptec Corporation of California is out
to get you. A directional microphone, mounted up to 100 metres away, picks up
all the sounds near a wall. The device continually compares what it hears with
stored recordings, such as the rattle of a spray can or the squeal of a felt
marker pen. Meanwhile, an electronic nose near the wall checks for paint
vapours, and infrared detectors register body heat (WO 00/75899). When the
device detects the smells and noises of a graffiti artist it drops a cage on the
offender and calls the police.