StorageTek L180 Reference Manual page 22

Controls and Indicators
Function Select Indicator
Indicates which user programmable parameter is selected for status display
or modification. Use the left Select button to cycle through the five user
selectable options above.
Function Status Indicator
Indicates the state of the selected user programmable function. Use the right
Select button to cycle among the choices.
AC Source Indicator
AC Source
Indicates the line quality and select status of each source.
B A
Indicators:
Bright = source selected
Dim = source okay, but not selected
Off = source is not okay
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