NorthStar Echo Sounder 491 Operation Manual page 27

Entering numerical
values
491 Echo Sounder Operations Manual
When changing the numerical value of the echo sounder's
settings, you can either press the CURSOR PAD to increase or
decrease the value, or use the KEYPAD to manually type in
the desired value.
961/962 echo sounder setup screen
957/958 echo sounder setup screen
Page 23