Fujitsu ScanSnap S1500M Operator's Manual page 219

Using the ScanSnap in Various Ways (for Windows Users)
5.
Press the [Scan] button on the ScanSnap to start a scan.
When you select [Simplex scan] from the Right-Click Menu, scanning is performed in
simplex mode even if [Duplex Scan (Double-sided)] is specified for [Scanning side] in the
[Scanning] tab.
Scanned image is saved.
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