Printers: Impact vs. Non-Impact Technology Explained
Understanding Printers and Their Types
Printers are output devices used to produce permanent output on paper. Printers can be divided into two main categories:
Impact Printers
Impact printers use hammers or pins that strike against a ribbon and paper to print text. This mechanism is known as electro-mechanical. There are two main types:
Character Printers
Character printers print one character at a time and have a relatively slower speed. An example is the dot matrix printer.
Dot Matrix Printers
Dot matrix printers print characters as a combination of dots. They are popular serial printers with a matrix of pins on the print head that form the characters. The computer memory sends one character at a time to be printed. A carbon ribbon is positioned between the pins and the paper, and the words are printed when the pins strike the carbon. These printers generally have 24 pins.
Line Printers
Line printers are impact printers used with mini and mainframe computers for producing large volume outputs. Their speed ranges from 300 to 3000 lines per minute (LPM). Examples include drum printers and chain printers.
Non-Impact Printers
Non-impact printers use technologies such as ink-jet or laser. They provide better output quality at higher speeds. These printers are of three types:
Laser Printers
Laser printers use a laser beam to produce an image on a drum. The laser light alters the electrical charge on the drum wherever it hits. The drum is then rolled through a reservoir of toner, which is picked up by the charged portions. Finally, the toner is transferred to the paper through a combination of heat and pressure.
Ink-Jet Printers
Ink-jet printers print characters by spraying patterns of ink on the paper from a nozzle or jet. They print from nozzles with very fine holes, from which a specially made ink is pumped out to create various letters and shapes. The ink emerges from the nozzle in vapor form and, after passing through a reflecting plate, forms the desired letter/shape at the desired place.
This process is similar to how copy machines work. Because an entire page is transmitted to a drum before the toner is applied, laser printers are sometimes called page printers. There are two other types of page printers that fall under the category of laser printers even though they do not use lasers at all. One uses an array of LEDs to expose the drum and the other uses LCDs. Once the drum is charged, however, they both operate like a real laser printer. One of the chief characteristics of laser printers is their resolution—how many dots per inch (dpi) they lay down.
The available resolutions range from 300 dpi at the low end to 1,200 dpi at the high end. In addition to text, laser printers are very adept at printing graphics. To print a full-page graphic at 300 dpi, significant amounts of memory are needed in the printer to print high-resolution graphics.