1-29 TM106601_(7/01)
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OMMAND
YSTEMS
IVISION
the first frame pulse and establishes the beacon range as previously described. The final pulse,
occurs 15 µsec after the first pulse; this is the other framing pulse. The pulses between the first and
last pulse establish the beacon code. Table 1.6-5 lists all the possible pulse combinations. Observe
that a condition exists for a zero code, when only the two frame marks would be transmitted. This
zero code reply is reserved for fault indications.
When an unknown beacon reply appears on the screen while flying in the BCN mode, the reply can
easily be identified by stepping through the beacon codes with the PUSH CODE button until the
selected code appears in the beacon symbol on the screen. If both a 2-pulse reply and a 6-pulse reply
are being received and the two beacons are assigned the same code (e.g. B3), they can still be
identified, since only the beacon replies that agree with the format selected by the BCN button will be
identified on the screen.
Note
+ Range must be set between 40 miles maximum
and 2 miles minimum for DO-172 beacon
identification to function. No decoding will
occur beyond 40 miles or under 2 miles
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