Furuno GP-3500F - Manual (Page 190)

11. VIDEO SOUNDER OPERATION
11-18
11.6 Entering Mark on the Display
You can mark on the plotter (or pilot) display through the sounder display.
● Press appropriate numeric key among 1 through 7 at the moment a fish
school, etc. appears on the sounder screen.
The sequence is as below depending on the display in use.
Sounder display
A vertical bar is entered at the right edge of the echo sounder screen. The color
of this bar depends on the number of display colors used. It is the second color
from the top of color bar in the 16-color display, or the top color in the 8-color
display.
On the plotter display, the selected mark is entered at ship’s position the moment
the key is pressed.
Plotter (or pilot)/sounder display
A vertical bar is entered at the right edge of the echo sounder screen. The mark
is entered on the plotter (or pilot) display as below.
When the cursor is turned on: at the cursor position
When the cursor is turned off: at own ship’s position