Sunday, February 24, 2008
Sunday, February 17, 2008
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 Dot-matrix printers are now (as of 2005) quickly being superseded even as receipt printers.
Sunday, February 10, 2008
Printers are routinely confidential by the underlying print technology they employ; numerous such technologies have been developed over the years.
The choice of print engine has a considerable effect on what jobs a printer is suitable for, as various technologies are capable of different levels of image/text quality, print speed, low cost, noise; in addition, some technologies are inappropriate for certain types of physical media (such as carbon paper or transparencies).
Another aspect of printer technology that is frequently forgotten is resistance to alteration: liquid ink such as from an inkjet head or fabric ribbon becomes absorbed by the paper fibers, so documents printed with liquid ink are more difficult to alter than documents printed with toner or solid inks, which do not penetrate below the paper surface.
Checks should also be printed with liquid ink or on special "check paper with toner anchorage". For similar reasons carbon film ribbons for IBM Selectric typewriters bore labels counsel against using them to type negotiable instruments such as checks. The machine-readable lower portion of a check, however, must be printed using MICR toner or ink. Banks and additional clearing houses employ automation equipment that relies on the magnetic flux from these specially printed characters to function properly.
Tuesday, February 05, 2008
Cybernetics is the interdisciplinary study of the structure of complex systems, particularly communication processes, control mechanisms and feedback principles. Cybernetics is strongly related to control theory and systems theory.
Contemporary cybernetics began as an interdisciplinary study linking the fields of control systems, electrical network theory, mechanical engineering, logic modeling, evolutionary biology and neuroscience in the 1940s. Other fields of study which have partial or been influenced by cybernetics include game theory, system theory (a mathematical counterpart to cybernetics), psychology (especially neuropsychology, behavioral psychology, and cognitive psychology), and also philosophy, and even architecture.