Oki MC160n - Manual (Page 34)

34 Control Panel and Configuration Menu
Select Tray Settings TRAY1 / TRAY2
Select which paper tray can be used to supply paper
when printing received documents or transmission
reports. A paper tray that cannot be used for
supplying paper can also be specified.
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If an optional lower feeder unit is not installed,
SELECT TRAY cannot be set.