Samyung NAVIS800FS Instruction Manual page 66

2.2.6 Fish Alarm
This is a function to make an alarming when the equipment senses any fish school under voyage.
 Press ) button and move [2.SET]  [2.ALARM SET]  [6.FISH ALARM].
(
 Use
( ) button to select [ON] / [OFF] and the signals of fish school as [Low], [Mid], [High].
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