What do the different light patterns mean on the HP LaserJet M109/M112?

The printer uses different light patterns to indicate its status. A steady light means the printer is ready, while a specific pattern indicates it is processing a job. Other patterns indicate an error, manual feed, manual duplex, cartridge very low, or out of paper, and another pattern signals the printer is initializing, cleaning, or cooling down. For a complete list of light patterns, refer to the user guide at hp.com/support. (Page 2)