Avidyne IFD540 Pilot's Manual page 164

The depiction on the map when in OBS mode depends on
whether the system determines if the airplane is in TO or FROM
orientation.
In OBS TO (defined as the when the difference between the
selected OBS course and the aircraft course to the fix is < 90),
the map will display only the magenta leg to be flown to the fix.
There is no white leg depiction for the outbound leg because the
assumed intent is to fly to the fix and automatically sequence legs
as normal from there.
OBS TO Depiction
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