a reproduction machine adapted for producing copies of an original on either or both sides of a copy sheet and forwarding the finished copy to a collator . to collate the produced copy in the proper orientation , an inverter - reverser is employed to allow single - sided copy to pass directly to the collator , route single - sided copy to a secondary feed tray for subsequent processing to allow copying on the reverse side of the sheet to produce duplex copies , and for inverting duplex copies prior to delivery to the collator to provide the required sheet orientation in the collator .