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.