Furuno FCV-1200L Operator's Manual page 30

Ship's speed dependent mode
With speed data provided by a speed log, current indicator or navigation equipment, the display
advance speed may be set according to ship's speed, the ship's speed dependent mode. As
shown in the figure below the horizontal scale of the display is not influenced by the change of
ship's speed, thus the speed-dependent picture advance permits judgement of fish school size
and abundance at any speed. The picture advance speed indication is suffixed with an "S" when
the ship's speed dependent mode is active. For example, "1/1S." For how to enable the ship's
speed dependent mode see page 2-9. This function is available with ship's speed of 2-20 kt.
Same size
fish schools
FULL SPEED
Speed
Actual Movement
1-20
HALF SPEED
How the ship's speed dependent mode works
Normal Mode
Ship's Speed Dependent Mode
Fish school is shrunk at high
ship's speed; expanded at
low ship's speed.
Fish schools are shown
same size regardless of
ship's speed.