Furuno FSV-25 Operator's Manual page 55

9. Rotate the trackball clockwise to select the ending point then push the left button.
The display paints a fan-shaped alarm zone.
The alarm range appears on the display as shown below.
10. Long-push the MENU/ESC key to close all menus.
When a fish echo enters the alarm area the buzzer sounds.
Note 1: There must be at least 3° difference between the starting and ending points
to get a fan-shaped alarm zone as shown in (a) and (b) below. Otherwise, the unit
paints a 360° alarm zone as in (c) where there is less than 3° between the starting and
ending points.
(a)
<< Alarm Zone >>
Move trackball cursor to origin of
alarm zone and left click.
Press [R/B] key or right click to cancel.
<< Alarm Zone >>
Move cursor to the end of alarm
range and left click.
Press [R/B] key or right click to cancel.
Fish alarm range
More than 3° Within 3°
(b) (c)
2. HORIZONTAL MODE
2-25