Duplex scanning is a feature of computer scanner

Image scanner

In computing, an image scanner—often abbreviated to just scanner—is a device that optically scans images, printed text, handwriting, or an object, and converts it to a digital image. Common examples found in offices are variations of the desktop scanner where the document is placed on a glass...

s and multifunction printers (MFPs)

Multifunction printer

An MFP , multifunctional, all-in-one , or Multifunction Device , is an office machine which incorporates the functionality of multiple devices in one, so as to have a smaller footprint in a home or small business setting , or to provide centralized document...

 that allows the automatic scanning of a sheet of paper on both sides. Devices without this capability can only scan a single side of a sheet of paper at a time.

In general, duplex scanning is achieved on multifunction printers

Multifunction printer

An MFP , multifunctional, all-in-one , or Multifunction Device , is an office machine which incorporates the functionality of multiple devices in one, so as to have a smaller footprint in a home or small business setting , or to provide centralized document...

 using a Reversing Automatic Document Feeder

Automatic Document Feeder

In multifunction or all-in-one printers, fax machines, photocopiers and scanners, an automatic document feeder or ADF is a feature which takes several pages and feeds the paper one page at a time into a scanner or copier, allowing the user to scan, and thereby copy, print, or fax, multiple-page...

(RADF). Duplex scanning is achieved on computer scanners by either RADF or by single pass duplex scanning using two cameras; one for the front side of the document and one for the back side of the document.

On MFPs

Multifunction printer

An MFP , multifunctional, all-in-one , or Multifunction Device , is an office machine which incorporates the functionality of multiple devices in one, so as to have a smaller footprint in a home or small business setting , or to provide centralized document...

, it is common to find duplex scanning on devices that also have duplex printing

Duplex printing

Duplex printing is a feature of computer printers and multifunction printers that allows the automatic printing of a sheet of paper on both sides...

capabilities.

Typical duplex scanners

The following table compares features for a number of popular duplex scanners:

product	dimensions (mm)	dpi	pages per minute (color)	max page size	interface
Fujitsu fi-6130 A4 Series Scanner	301 x 160 x 158	600	30	A4	USB 2.0
Plustek MobileOffice D28 Corporate	303 x 94 x 60	600	28	A4	USB 2.0
Xerox Travel Scanner 100	289 x 51 x 38	600	4	A4	USB 2.0
ScanShell 3000DN	300 x 50 x 45	600	3	A4	USB 2.0
Canon imageFORMULA P-150	280 x 95 x 40	600	10	216mm x 356mm	USB 2.0
Canon DR-2080C	298 x 209 x 99	600	36	216mm x 355mm	USB 2.0
HP Scanjet 7650	482 x 340 x 162	2400	12	216mm x 305mm	USB 2.0