Furuno COLOR VIDEO PLOTTER 1933C - Manual (Page 150)

4. VIDEO SOUNDER OPERATION
4-6
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.
200k
80
This part
is zoomed.
Fish
school
Zoom marker
NORMAL DISPLAY BOTTOM-LOCK
DISPLAY
50
0
100
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10
8
6
4
2
0
10
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Bottom-lock display plus normal sounder display