Dell 3110cn Color Laser Printer - Manual (Page 327)

Removing the Optional Duplexer
NOTICE: Make sure nothing touches or scratches the surface (black-colored film) of the belt unit.
Scratches, dirt, or oil from your hands on the film of the belt unit may reduce print quality.
NOTICE: To protect the drums of the print cartridges against bright light, close the front cover within
5 minutes. If the front cover remains open for more than 5 minutes, print quality may deteriorate.
Make sure that the printer is turned off and unplug the power cord from the rear of the printer. 1.
Push the side button and open the front cover. 2.
Pull up on the belt release levers and rotate the belt unit up as shown in the illustration. 3.