HP Color LaserJet 4730 Multifunction Printer series - Manual (Page 192)

Output accessory bridge
The output accessory bridge is required if a 3-bin mailbox or a stapler/stacker is installed on the MFP.
The output accessory bridge is a pathway between the MFP and the output device. For more information
about installing the output accessory bridge, see the Installation Guide. For information about clearing
paper jams in the output accessory bridge, see
Clearing jams .
1 Output accessory bridge
2 Stapler/stacker
3 3-bin mailbox
172 Chapter 9 Optional output devices ENWW