The operator's manual is a generic manual that covers all of the 5 series units. It has a hodgepodge of information on the various units but nothing specific for the unit in the box it came with. You are correct in your assessment that the DSI units have very few options as far as changing settings. There is no sensitivity setting, only contrast. The color settings really don't how different colors for different sonar returns, they are simply a color preference option. You can pick from several of your favorite background colors. Personally, I believe the gray scale is as good as any of the others and that really makes the colors simply a decoration rather than a useful tool. There is nothing in the operator's manual that tells you anything about the frequency settings other than how to choose them. It doesn't tell you where you should use one or the other, it doesn't tell you anything about the transmission angle for each frequency. The majority of the manual is about the chart options. Not much at all on the Sonar.
Here is a link to the operators manual for anyone interested: You will notice a disclaimer on page one saying that the manual is for several different units and your unit's capabilities may differ from what you see here. You would think for $650 they could print a manual specifically for the unit in the box.
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