Depth Lines (Advanced); Noise Filter (Advanced) - Humminbird 858c Installation And Operation Manual

Depth Lines
(Advanced)
Settings: Off, On; Default = On
Depth Lines divide the display into four equal sections which are separated
by three horizontal depth lines. The depth of each line is displayed along the
depth scale. You can turn Depth Lines On or Off.
Depth Lines
Noise Filter adjusts the sonar Noise Filter to limit interference on the display
from sources such as your boat engine, turbulence, or other sonar devices.
The Off setting removes all filtering. Low, Medium, and High1, High2, High3
settings add progressive filtering of the sonar returns. High1, High2, and
High3 are useful when there is excessive trolling motor noise, but in some
deep water situations, the High settings may actually hinder your unit's
ability to find the bottom.
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Noise Filter
(Advanced)
Settings: Off, Low, Medium, High1, High2, High3;
Default = Low
Sonar Menu Tab