Agilent Technologies 54810A User's Quick Start Manual page 69

Using the Oscilloscope
To reinitialize the oscilloscope
keypad that allows you to set a particular trigger level. You can also click
on the up and down arrows to the right of the setting to increase or
decrease the trigger level, respectively. Or, you can click on the trigger
reference indicator at the right side of the display and drag it up or down
to change the trigger level.
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