Furuno 851 MARK-2 - Manual (Page 37)

3-7
3.7 Racon (Radar Beacon)
A racon is a radar transponder which emits
a characteristic signal when triggered by a
ship’s radar (usually only the 3 centimeter
band). The signal may be emitted on the
same frequency as that of the triggering
radar, in which case it is superimposed on
the ship's radar display automatically.
The racon signal appears on the PPI as a
radial line originating at a point just beyond
the position of the radar beacon or as a
Morse code signal (see figure below)
displayed radially from just beyond the
beacon.
Racon
Figure 3-9 Appearance of racon signal
on the display