Humminbird Ultima Operation Manual page 16

2. Setting Depth Range;
Factory setting: On (Automatic)
When you turn the Ultima on, it finds the
bottom, sets the ideal depth range, and automatically
adjusts the depth range (to as much as 185 meters)
as the depth changes. In this "Auto Depth Range"
mode, the bottom is blacked-in for easy-to-
understand readings.
If you prefer, you can turn Auto Depth Range
off. Select DEPM RANGE, press ON-OFF, and adjust
the Depth Range with the UP or DOWN arrow key.
In this "Manual Depth Range" mode, the
bottom is not blacked in.This lets you see a "second
return," which is preferred by some fishermen because
the width of the second echo can indicate bottom
hardness.
3. Enabling Bottom Alarm;
Factory setting: OFF
The Bottom Alarm lets you specify the minimum
depth you want to maintain. To use it, select Bottom Alarm;
then, press the ON-OFF button to activate the alarm, and
the UP or DOWN arrow key to adjust the depth at which the
alarm will sound. An alarm symbol is displayed when this
function is on.
When Bottom Alarm is on, you'll hear a continuous
chirping sound when the bottom is shallower than you
defined. This is very handy for alerting you to shallow water
or helping you to maintain position over structure.
NOTE: The Ultima should not be used as a navigation aid to
prevent collision, grounding, boat damage or personal
injury.