Oki PT390 Manuel D'utilisation page 10

Note: Red or blue printing on two-color thermal paper has an inferior preservation
characteristic that is equivalent to that of normal thermal paper.
Note :Printouts on label paper or thick paper may contain blurs or voids, depending
on the humidity and other environmental conditions. Adjust the print speed
and print density as appropriate for the type of paper used. (See "C-3 Setting
Up the Printer" in Appendix C, "Special Modes.")
In particular, note that the paper transport accuracy may be negatively
affected by printing a barcode in the top margin at the beginning of paper
transport or in the Lower margin at the end of paper transport.
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