491 Echo Sounder Operations Manual
Page 57
4. Follow the instructions below for each of these five
settings.
Fish alarm window
Setting the alarm’s
echo strength level
To set the fish alarm’s minimum echo-strength level:
1. At the
FISH ALARM
window, press
SET ALARM LEVEL
.
2. Press the
CURSOR PAD
up and down to set the echo
strength level from 1 to 15, as represented on the vertical
color bar.
Echoes received that are strong enough to be within the
crosshatched area on the vertical bar will cause an alarm
(weaker echoes will be ignored).
Setting the upper
and lower marker
depths
The fish alarm will sound only when there are echoes inside
(or optionally, outside) the upper and lower markers. These
markers are displayed on the
ECHO
screens.
To set the depth of the upper marker:
1. At the
FISH ALARM
window, press
SET UPPER MKR
.
The upper marker window is highlighted in black.