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491 Echo Sounder Operations Manual Page 31
desired signal range, Signal Level completely removes the
weaker colors and their echoes.
To adjust the signal level:
1. On the ECHO screen, press PICTURE.
2. On the PICTURE screen, press SIGNAL LEVEL.
3. At the SIGNAL LEVEL window, press the CURSOR PAD
up or down to remove the weaker color levels from the
picture, or use the KEYPAD to manually enter the desired
signal level.
The available settings range from 1 (minimum) to 5 (max-
imum). For example, if you select a signal level of 3, echo
strengths of 0 through 3 are all displayed using the same
color.
4. Press RETURN to go back to the ECHO screen.
Suppressing interference (the noise limiter)
The noise limiter reduces the adverse effects of interference
from other nearby echo sounders or electronic devices.
however, the noise limiter may cause some very weak echoes
to be made smaller or entirely eliminated, since it removes any
echoes that aren’t sustained for at least two pings.
To turn on the noise limiter:
1. At the ECHO screen, press PICTURE.
2. At the PICTURE screen, press NOISE LIMITER.
3. At the NOISE LIMITER window, press the CURSOR PAD
up to turn the noise limiter on (or press NOISE LIMITER
again).
4. Press the RETURN key to go back to the ECHO screen.
Turning the noise limiter on changes a portion of the
PICTURE key tab from green to yellow, as a reminder.