Furuno COLOR VIDEO PLOTTER 1833C Operator's Manual page 150

4. VIDEO SOUNDER OPERATION
Bottom-lock display
The bottom-lock display provides a compressed normal picture on the right half
of the screen and a 10 or 20 feet (3 or 6 meter) wide layer in contact with the
bottom is expanded onto the left half of the screen. This mode is useful for
discriminating bottom fish from the bottom echo. You may select the bottom lock
range from the SOUNDER RANGE SETUP menu. For details, see paragraph
5.9.3.
4-6
10
8
Fish
school
6
4
2
10
80
0
BOTTOM-LOCK
DISPLAY
Bottom-lock display plus normal sounder display
0
- -
-
-
-
-
-
- -
-
-
50
- -
-
-
- -
-
-
-
- -
100
-
-
-
200k
NORMAL DISPLAY
Zoom marker
This part
is zoomed.