Furuno GP-3500F - Manual (Page 179)

11. VIDEO SOUNDER OPERATION
11-7
11.2.8 Mix display
This mode compares echo intensity between low and high frequencies, and
displays echoes from tiny fish in discriminative colors. This is done by utilizing
the fact that tiny fish return a stronger echo against a high frequency rather than
a low frequency. This is done as below.
1. If a high frequency echo is stronger than the corresponding echo on the low
frequency, the high frequency echo is displayed.
2. If the low frequency echo is stronger than or equal to the high frequency
echo, it is less likely to be a tiny fish and therefore is displayed in blue.
3. If the echoes on both frequencies have the intensity corresponding to reddish
brown or red, they are displayed in reddish brown or red: this is necessary to
display the zero line and bottom in reddish brown or red.
In other words, the echoes displayed in orange thru light-blue may be
considered to be tiny fish such as whitebait.
R-BRN
Low frequency High frequency
RED
YEL
ORG
GRN
Green Blue
YEL
Blue
+
Discriminator
BLU
Reddish-brown
These echoes are
likely to be small fish.
Displayed in blue
since high freq.
echo is weaker.
Displayed in
reddish-brown since
high freq. echoes
are red or reddish-
brown.
How the mix display works