What is automatic document feeder?
An automatic document feeder (ADF) is a feature found in a printer, photocopier, fax machine, or scanner where a stack of paper is loaded into the machine and then automatically fed through it so that the user can print, scan, or copy any page in without manual input the machine.
There are two types of ADFs that can be used for duplex scanning:
Reverse Automatic Document Feeders (RADF) scan one side of the page, and then flip the paper over so the other side can be scanned.
Duplex automatic document feeders (DADF) scan both sides of the page in a single pass.
An ADF is a standard feature on most printers, fax machines, and large photocopiers, but scanners typically do not have ADFs, although they may have them as add-ons. Flatbed scanners are designed without ADFs.