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Old 11-Nov-2014, 6:27 PM   #9
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Join Date: Sep 2012
Posts: 472
Originally Posted by ADTech View Post
Many commercial door openers back in the day used X-band radar for motion sensing. Used to set of 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.
Yes, it has been at least 25 years, since I've used one too.

I even remember using the old separate TX/RX ultrasonic motion sensors, that you could actually hear.
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