HP Deskjet 9800 Printer series - Manual (Page 19)

Optional automatic two-sided printing accessory (duplex unit)
The printer can automatically print on both sides of a sheet of paper when the duplex unit is attached
to the back of the printer. (See
Installing the optional automatic two-sided printing accessory (duplex
unit) .)
NOTE The duplex unit is a standard part in the HP Deskjet 9800d, 9803d, and 9808d
printers. It may be purchased separately in some countries/regions.
1 Rear cover
2 Release buttons for the duplex unit
3 Release buttons for the rear cover of the duplex unit to clear a paper jam
Understanding the printer parts and functions 9