1. A device for printing images on halves of both sides of a receiving sheet, said device comprising: (a) a printing station; (b) a sheet conveyor path through the printing station; (c) a sheet turn-over path following the conveyor path for re-feeding a sheet to the printing station; (d) a sheet discharge path following said conveyor path; (e) sheet conveyor means for conveying sheets in said paths; (f) a sheet deflector having a first position to guide a sheet from said sheet conveyor path into said turn-over path and a second position to guide said sheet from said sheet conveyor path into said discharge path; (g) first control means for holding said sheet deflector in said first position during three consecutive passes of a sheet through the sheet conveyor path and in a second position during a fourth pass of the sheet through said sheet conveyor path; and (h) second control means for printing an image on one half of the sheet in said first and fourth passes of said sheet and for printing an image on the other half of the sheet in the second and third passes of said sheet.