491 Echo Sounder Operations Manual
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491 Features and Specifications
Table 4: 491 echo sounder features
Performance characteristics
Output
Single/Dual Channel, 50/200kHz, 600W
Alarms
Fish, seabed, temperature
Update rate
10 Hz maximum (depends on water depth)
Auto modes
Fishing and cruising
Zoom modes
Marker, bottom, bottom lock, bottom lock/center
Features
Mark present or past echo as waypoint (961/962)
Go directly to any past echo
A-scope analyzes present or past echoes
Navigation data shown at bottom of screen
Demo mode for training