Furuno FCV-1200L Operator's Manual page 16

ZOOM
The "single picture" (high or low frequency) appears on the right 1/2 of the screen and the zoom
picture on the left 1/2. The zoom picture may be selected among BOTTOM LOCK, BOTTOM
ZOOM, MARKER ZOOM, DISCRIM (discrimination) 1/2 and DISCRIM (discrimination) 1/3. The
default zoom picture is BOTTOM LOCK. You can select through the menu. See page 2-3.
BOTTOM LOCK
The bottom lock display shows the area between the zoom marker and the bottom as a straight
line to distinguish it from fish near the bottom, and thus it is useful for discriminating fish near
the bottom.
Bottom lock display
Zoomed fish school
Bottom as a straight line
1-6
1/1
LF
5
4
3
2
Fish
1
school
21.7
ft
0
Bottom lock display
0
0 0
Zoom marker
10
This area zoomed
and displayed on left
20 1/2 of screen.
30
Single frequency display
40