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Old 26th August 2012 | 14:03
  #18 (permalink)  
172driver
 
Joined: Jul 2005
Posts: 1,929
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From: SoCal
it certainly has the rectangular orange 'activity' light, (which flickers all the while, in flight and even on the ground)
FYI, this light tells you your transponder is being interrogated by radar. In a busy radar environment this can mean it's flickering pretty much all of the time.

When pressing the IDENT button it stays on without flickering for a second or so, at least it does on all the units I've ever used.

Now, you may ask, 'why do I need to know that my transponder is being interrogated?' The most important reason IMHO is to warn you of a duff unit. IOW if you are flying in airspace you know is radar controlled and the light stays off, you most likely have a problem - and it's a good idea to communicate with ATC to sort that out. Usually, btw, cycling the transponder does the trick.
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