Brother MFC-L6750DW User Manual page 62

Difficulties
Received faxes
appear as split pages.
Dialing does not work.
(No dial tone)
Poor sending quality.
Vertical black lines
when sending.
Suggestions
Turn on Auto Reduction.
Check all line cord connections.
Change Tone/Pulse setting. (Available only for some countries)
Try changing your resolution to Fine or S.Fine.
Make a copy to check your machine's scanner operation. If the copy
quality is not good, clean the scanner.
For more information, see the Online User's Guide: Clean the Scanner.
Black vertical lines on faxes you send are typically caused by dirt or
correction fluid on the glass strip.
For more information, see the Online User's Guide: Clean the Scanner.
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