Humminbird LCR 120 Operation Manual page 30

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 DEPTH
RANGE, press ON-OFF, and adjust the Depth Range with the Up or Down
arrow button.
In this "Manual Depth Range" mode, the bottom is not blacked in.
This lets you see a "second return," which is preferred by some fisherman
because the width of the second echo can indicate bottom hardness.
Trip Log
10. Trip Log
Factory Setting: Off
Although speed and temperature accessories are not available for the
LCR 120, the Trip Log provides a useful timer. The timer begins when the
unit is powered and can be reset and any time by pressing STOP.
Pressing ON-OFF exits Trip Log and returns you to normal LCR 120
operations.