Door Motion Alarm
(490-0419)                   Hints and Tips           Faxback Doc. # 32139

Q:  What is the nature of the motion detector?  What inside makes it work?

A:  Motion detectors are security devices that detect motion.  The
    photoelectric eye is a narrow visible light beam that is aimed across
    an area that shines directly into a photoelectric eye.  When the beam
    is interrupted, an alarm sounds.  Ultrasonic sound sensors emit a
    burst of high frequency sound and then "listen" for an echo.  Changes
    indicate a movement around an area and an alarm goes off.  Passive
    infrared detectors sense motion in a zone of coverage and sound an
    alarm with respect to temperature and movement.  The IR light is
    reflected from a moving object that has temperature (approx 98 Degrees
    body FG) to sound the alarm.


(IR-04/22/96)