Various types of unsupervised batch scanning are also possible with a minimum of support needed in the back end (driver). Many scanners support the attachment of document feeders which allow a large number of sheets of paper to be automatically scanned in succession. Using the SANE API, the front end simply has to "play back" the same set of options for each scan, driving the document feed in between scans to load the next sheet of paper. The front end only has to obtain the set of options from the user once.