Specifications

print head contains a matrix of metal pins (usually either 9 or 24) that it extends in various combina-
tions to make a physical impression on the paper. Between the pins and the paper is an inked ribbon,
much like that used in a typewriter. The pins pressing through the ribbon onto the page make a series
of small dots, forming typographic characters on the page. Dot-matrix printers also usually have rudi-
mentary graphical capabilities, enabling them to produce low-resolution bitmaps using their limited
memory as a band buffer.
Dot-matrix printers usually are associated with continuous sheet paper, driven by pinholes on the
edges. Most models can also handle single sheets, although rarely with the accuracy found in most
laser or inkjet printers. Because they are impact printers, meaning that actual physical contact occurs
between the print head and the paper, dot-matrix printers can do one thing that lasers and inkjets
can’t: print multipart forms and carbon copies. Many printers enable you to adjust the pressure of the
impact to support various numbers of copies. Dot-matrix printers are rarely used for correspondence
and general office printing anymore. Instead, they have found their place in commercial applications,
such as for banks, hotels, auto and appliance parts stores, and warehouses.
Note
Visit the Epson Web site for an interactive product finder for its impact printers. Okidata offers a similar service, which
also includes its LED printers and fax machines. Both of these services will ask you detailed questions about your printer
requirements and match your answers to the models that fit your requirements most closely.
Color Printing
A number of competing technologies are available for color printing aside from the nearly universal
inkjet printers found at home and at the office. Other technologies include color laser and LED print-
ers, solid-ink printers, and dye-sublimation printers. Color printing, once limited to only expensive
graphic arts use, now spans the entire price range of printers—from slow inkjet printers under $100 to
high-speed, 1,200dpi PostScript laser, LED, and solid-ink printers that cost $2,500 or more. This sec-
tion covers the various color printing technologies in detail to help you decide whether you need
more than an ordinary inkjet printer provides for color output.
Several types of color printers are available; most of them are adaptations of existing monochrome
technologies. In most cases, color printers function by using the same printing medium in several col-
ors (usually four). Thus, a color inkjet printer or color solid-ink printer uses four or more colored inks,
and a color laser uses toner in four colors. As in process color offset printing, virtually any color can
be created by combining cyan, magenta, yellow, and black in various proportions. This is called the
CMYK color model and is referred to as four-color printing. In the past, some very inexpensive inkjet
printers used only three colors, eliminating the black. These printers create a simulated black (often
called process black) by combining the maximum proportions of the other three colors, but the result
is far less effective than a true black medium, as well as costly. If you still are using a single-cartridge
inkjet printer, you’ll find that even the cheapest of today’s dual-cartridge models produces better print
quality for both black and color images without the hassle of flipping ink cartridges in and out of the
printer. Because a true black is available at all times, you also will save money by needing to replace
the color cartridge far less often. Depending on the color medium, various processes exist for combin-
ing the four colors (see Figure 8). Most color printers can’t actually mix the four colors to achieve the
desired result as you would mix paint. Instead, the printer applies the four colors very close to one
another in the correct proportion to achieve the desired result. For example, an inkjet printer works
by creating an interlaced pattern of dots, with each dot using one of the four inks. This is known as
bilevel printing. The proportion of dots of each color and the pattern in which they’re interlaced dic-
tates the final color. This process of mixing different-colored dots to form another color is called
dithering. The process is similar to the display on your color monitor that creates the color for each
pixel by placing red, green, and blue dots of varying intensities very close to one another.