HP 220240 - Manual (Page 39)

The following restrictions apply during printing in duplex mode:
• You cannot feed envelopes.
• You cannot feed paper manually.
2.7.1 Duplex Printing Printer Setup
Use the following procedure to set the printer up for duplex printing.
1. Set the printout selector to the duplex print position.
MLO-005128 (Figure 2-13; 16 picas)
2–12 Operator’s Guide