Furuno FAR-2107 Series Service Manual page 368

4) Display of Position Data and Ship Speed Data Box
When the position data and ship speed data are invalid, the data is displayed in red.
The conditions for it are as shown below.
The data varies with the input sentences. See p.3-4 for details.
HDG
SPD
SB 0.0 kt
COG
SOG
OS POSN
DGPS
Heading
Speed, Source
Log Speed
Course over Ground
Speed over Ground, Source
Position
Fig. 6.1.10 HDG/SPD/POS Display
6-12
When data is invalid in VBW
The mode is No Fix, DR, Manual
or SIM mode in GGA, GLL, VTG
and RMC.
6.1 Self-test