Skip to Content Information Center
Lexmark X850

Lexmark X850

Simplex Fax Is Run as a Duplex Through the ADF



This article explains why the scanner looks as though it is scanning both sides of the page when scanning one side only.

What you will see

When scanning a page, the scanner scans one side of the page, Then, when that page is ready to exit, it pulls the page back in to scan the other side before ejecting the page.


When Original Size is set to Mixed Sizes, the multifunction printer (MFP) cannot tell the size of any pages, so the paper size sensors will not be used. The MFP feeds the sheet through once to determine its size, then pulls it back and scans the page. It will repeat this behavior for each page, but will only scan the front side of the page. When Original Size is set to Auto Size Sense, the MFP uses the paper size sensors to determine the size of the first page and will then assume this size for the remaining pages.

To change this behavior:

If you do not want this to happen when you fax pages, review the settings listed in the table below.

Step Action Illustration
1Go to the Web page of the printer. ...
2Click Configuration.
3Click Fax Settings.
4Click Analog Fax Setup.
5 Look under and check the following: Duplex = On. The receiving fax machine will receive both the front and back of each page. Original Size = Mixed Sizes. If the sent fax contains only one page size, change this setting to Auto Size Sense.

Still have questions?

Please contact Lexmark Technical Support for additional information. NOTE: When calling for support you will need to know your printer model type and serial number. Please call from near the printer in case the technician on the phone asks you to perform a task involving the printer.



  • Infoprint 1540 MFP ----------------------------------------------------------------------------- Infoprint 1560 MFP ----------------------------------------------------------------------------- Infoprint 1580 MFP

Was this article helpful?