Apple AirPort Extreme 802.11n (4th Generation) - Manual (Page 16)

16 Chapter 2 AirPort Extreme Networks
Using the AirPort Extreme to Share a USB Printer
When you connect a compatible USB printer to your AirPort Extreme, supported
computers on the network (wired and wireless) can print to it.
It looks like this:
USB port
Shared printer
d
2.4 or 5 GHz
2.4 or 5 GHz