30 Aug
2008
30 Aug
'08
6:16 p.m.
In a few years - the early 1950s - the IFF sets were
SIF encoded,
where each aircraft or ship, when interrogated by a radar, would reply
with an octal pulse code 0000 to 3777. The interrogating radar would
then read the pulses, compare them to the code of the day, and modify
the video to the scopes automatically (AN/UPX-1, AN/APX-25, AN/UPA-24,
for those paying attention) to the operator could call the shots. I
think there are remnants of this ancient system still in use.
Aviation transponder squawk codes are the obvious ones,
octal, 0 -> 7777