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Old 11-Nov-2014, 12:56 PM   #8
Antennas Direct Tech Supp
Join Date: Jan 2010
Posts: 2,942
Door Openers and Alarm System Motion Detectors run off of Inferred
They see a difference in heat from the previous measurement
Many commercial door openers back in the day used X-band radar for motion sensing. Used to set off the radar detector from a 1/4 mile away from supermarkets and the like.

I haven't used a detector for almost 20 years, so I can't comment on what's currently in use, but I can confirm that radar frequencies were in use previously for this function.
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Last edited by ADTech; 11-Nov-2014 at 5:47 PM.
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