DUPLEX PRINTING

'Duplex printing' is a feature of computer printers that allows the automatic printing of a sheet of paper on both sides. Most printers can only print on a single side of paper automatically, this is sometimes called 'simplex printing'.
Duplex printers work by using a special ''Reversing Automatic Document Feeder'' (RADF), or a duplexing unit that reverses a piece of paper after the first side has been printed. This works in combination with a software solution on the computer that is printing to allow printing on both sides of the paper. Duplex printing is normally built-in to special double-sided printers; however some printers, e.g. the HP LaserJet 4, can be upgraded later on to duplex capability.
Duplex printers, depending on options, software and printer settings, can print single-sided page to single-sided page (1:1) or double-sided page to double-sided page (2:2). Many can also combine single-sided pages into a double-sided page format (1:2). Double-sided booklet formats (2:2 with a center fold) are also available, depending on optional outputs from the printer.
Simplex printers can still print duplex jobs; however, the user has to manually turn the print job over and re-initialize the printing of the document.