HP Deskjet 6840 Color Inkjet Printer - Manual (Page 16)

Note: It is recommended that you do not use the photo print cartridge or the gray
photo print cartridge for ink-backup mode.
Exiting ink-backup mode
Install two print cartridges in the printer to exit the ink-backup mode.
To install a print cartridge, see the
print cartridge installation page.
4.8 Automatic Paper-Type Sensor
The Automatic Paper-Type Sensor automatically selects the appropriate print
settings for the media that is being printed on, particularly HP media.
When the Automatic Paper-Type Sensor is engaged, the printer scans the first page
of a document with a red optical sensor light to determine the best paper-type
setting. After the printer determines the paper-type setting, the page is printed.
Do not place the printer in direct sunlight. Direct sunlight can interfere with the
Automatic Paper-Type Sensor.
To use the Automatic Paper-Type Sensor, see the
paper-type selection page.
Note: The Automatic Paper-Type Sensor is not available for documents that are
printed from the 250-Sheet Plain Paper Tray Accessory or the Auto Two-
Sided Print Accessory with Small Paper Tray .
HP Deskjet 6800 series printer User's Guide
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