NorthStar Navigation Echo Sounder NorthStar 491 - Manual (Page 63)

491 Echo Sounder Operations Manual Page 59
To set the bottom alarm:
1. At the ECHO screen, press MORE.
2. Press ALARM.
3. At the ALARM screen, press BOTTOM ALARM.
The options on the BOTTOM ALARM window are on/off
and the depth setting.
Bottom alarm window
Setting the bottom
level
You can set the depth level for the seabed, so that as soon as
the bottom is shallower than this depth, the bottom alarm will
sound.
To set the bottom level, at the BOTTOM ALARM window, press
the CURSOR PAD up or down to set the depth, or use the
KEYPAD to manually enter the desired depth.
NOTE:
The 491’s depth indicator reflects the depth below your vessel’s
transducer, not below the keel. Ask your installer for the exact dis-
tance between your transducer and your keel. This value must then
always be manually added to the 491’s depth indicator, or else
entered into the transducer’s depth setting on the
ECHO
SOUNDER SETUP screen for an automatically correct reading.