Furuno FCR-21x9-BB Operator's Manual page 248

11. CHART ALERTS
reference point is the conning position. Click the [ON] button to activate the own
ship check.
Bow
Stern
When an object having a Warning setting enters the Check Area, the object is high-
lighted in red and the aural alarm sounds.
Highlight (red)
11-4
Width
Ahead
Port Starboard
Distance
Object selected
for Chart Alert