NorthStar Echo Sounder 491 Operation Manual page 22

50 kHz echoes
Page 18
• when adjusting the picture, you can see the effect of
changes on the right side
200 kHz echoes
Figure 8: ECHO
To change the display frequency:
1. On the ECHO screen, press FREQUENCY until you
display the desired frequency or frequencies.
The frequencies in use are shown pictorially on the tab
just below the FREQUENCY key.
When you change the frequency, echoes already on the screen
don't change, they just move off the screen as they are
replaced by echoes at the new frequency.
A dual-frequency screen is split into two halves separated by a
gray vertical line in the center.
screen with both frequencies displayed
491 Echo Sounder Operations Manual
Adjusts the frequency
of the data displayed
(currently showing dual
frequency on a split
screen, with 50 kHz to
the left and 200 kHz to
the right)