Oki Microline 3320 Maintenance Manual page 51

(4) Top line print mechanism (See Figure 2-16.)
The front edge of the sheet is protected by the ribbon protector so that it can stop at a
position just near to the print head (0 tear off position) to start printing at the front end
of the sheet, without causing the sheet to crumple or curl up.
The printing starts at the front end of the sheet, and continues uni-directionally until the
front end of the sheet gets to the inside of the pull up roller cover.
After that, that printing continues bi-directionally.
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