Hitachi HT-4139-28 Developer's Manual page 7

Precautions for Use
Continuous scanning
If the application program does not support the continuous scanning, performance may
become lower than expectation.
If sheets are too thin, copy papers, with glue, or mixed sizes, multiple feeding error might
occur. Using options and/or the sheet check function, try to scan them correctly.
Scanned images
To confirm if the scanned data satisfy the level of customer's accuracy and quality, check
the gradation and density of scanned images.
This TWAIN driver does not support pre-view function.
Scanned data
This device can detect sheet sizes and multiple feeding but it might fail to catch multiple
feeding depending on conditions.
Inspect all scanned image data after scanning sheets and make sure that all sheets are
scanned correctly.
Extra attention is required when check will not performed or sheets will be discarded.
Imprinting (Numbering)
The imprinting is conducted after scanning but in some cases there might be imprinting
without image depends on operation of the application program.
There might be imprinting on wrong sheet due to multiple feeding error, etc.
Compare the original sheet and scanned data and ensure there are no missing images.
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