Furuno GP-3500F - Manual (Page 181)

11. VIDEO SOUNDER OPERATION
11-9
11.3 Automatic Sounder Operation
Automatic sounder operation is useful when you are preoccupied with other
tasks and do not have the time to adjust the display.
The automatic sounder function automatically selects the proper gain, range
scale and clutter suppression level according to depth. It works as follows:
• Range changes automatically to locate the bottom on the lower half of screen.
The range jumps to one step shallower range when bottom echoes reach a
half way point of the full scale from top and to one step deeper range when
they come to the lower edge of the scale.
• The gain is automatically adjusted to display the bottom echo in reddish brown
(default color arrangement).
• Clutter, which suppresses low level noise, is automatically adjusted.
Two types of automatic sounder modes are available: CRUISING and FISHING.
CRUISING is for tracking the bottom, and FISHING is for searching fish schools.
CRUISING uses a higher clutter rejection setting the FISHING therefore it is not
recommended for fish detection – weak fish echoes may be erased by the clutter
suppression circuit.