Epson Expression 1680 - Manual (Page 23)

Understanding EPSON TWAIN Pro Features 2-3
Selecting a Document Source
When scanning a reflective document placed on the document
table of the scanner, leave the Document Source set to
Flatbed .
Other selections are available depending on whether an optional
Automatic Document Feeder or Transparency Unit is installed.
Note:
Uninstalled options are not displayed.
Flatbed
Choose this setting to use the document table of the scanner.
Auto Document Feeder
Choose this setting to use the optional Automatic Document
Feeder.
Note:
Some applications do not support feeding and scanning more than one
sheet at a time.
TPU for Neg. Film, TPU for Pos. Film
Select one of these settings when using the Transparency Unit. If
you are scanning negative film, select
TPU for Neg. Film , and if
you are scanning positive film (or slides), select the TPU for Pos.
Film setting.