Sunday, February 17, 2008

Dot-Matrix Printers

In the common sense many printers rely on a matrix of pixels, or dots, that together form the larger image. However, the term dot matrix printer is specially used for impact printers that use a matrix of small pins to create precise dots. The advantage of dot-matrix over other collision printers is that they can produce graphical images in addition to text; however the text is generally of poorer quality than impact printers that use letterforms (type).

Dot-matrix printers can be generally divided into two major classes:

* Ballistic wire printers (discussed in the dot matrix printers article)

* Stored energy printers

Dot matrix printers can either be character-based or line-based (that is, a single horizontal series of pixels across the page), referring to the pattern of the print head. At one time, dot matrix printers were one of the more general types of printers used for general use - such as for home and small office use. Such printers would have either 9 or 24 pins on the make head, 24-pin print heads were able to print at a advanced quality. Once the price of inkjet printers dropped to the point where they were aggressive with dot matrix printers, dot matrix printers began to fall out of favor for general use.

Several dot matrix printers, such as the NEC P6300, can be upgraded to print in color. This is achieved through the use of a four-color ribbon mounted on a device (provided in an upgrade kit that replaces the standard black ribbon mechanism after installation) that raises and lowers the ribbons as needed. Color graphics are commonly printed in four passes at standard resolution, thus slowing down printing considerably. As a result, color graphics can take up to four times longer to print than regular monochrome graphics, or up to 8-16 times as long at high resolution mode.

Dot matrix printers are still usually used in low-cost, low-quality applications like cash registers, or in demanding, very high volume applications like invoice printing. The fact that they use an impact printing technique allows them to be used to print multi-part documents using carbonless copy paper (like sales invoices and credit card receipts), whereas other printing methods are unusable with paper of this type. Dot-matrix printers are now (as of 2005) quickly being superseded even as receipt printers.

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