Datasheet

80 Chapter 1
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Hardware
The LED printing process uses a row of small LEDs very close to the drum to expose it.
Each LED is about the same size as the diameter of the laser beam used in a laser printer.
Except for the writing stage, the operation is the same as the laser printing process.
LED printers are cheaper and smaller than lasers. However, they’re considered lower-end
printers, and they have a lower maximum dots per inch (dpi)—under 800dpi versus 1200 or
more for a laser printer.
Other Printer Technologies
Besides the aforementioned technologies, you may see a question or two about several less
popular ones on the A+ exam. They’re all high-end color graphics printers designed for
specialty professional usage:
Color Laser Works much like a regular laser printer except that it makes multiple passes
over the page, one for each ink color. Consequently, the printing speed is rather low.
Thermal Wax Transfer A color nonimpact line printer that uses a solid, wax-like ink. A
heater melts the wax and then sprays it onto the page, somewhat like an ink-jet. The quality
is very high, but so is the price ($2,500 or so). However, the wax is cheaper per page than
ink-jet ink. The quality is as good as a color laser, but the speed is much faster because it
needs only one pass.
Dye Sublimation Another color nonimpact line printer. This one converts a solid ink
into a gas that is then applied to the paper. Color is applied in a continuous tone, rather
than individual dots, and the colors are applied one at a time. The ink comes on film
rolls. The paper is very expensive, as is the ink. Print speeds are very low. The quality is
extremely high.
Printer Interfaces
Besides understanding the printer’s operation, for the exam you need to understand how
these devices talk to a computer. An interface is the collection of hardware and software
that allows the device to communicate with a computer. Each printer, for example, has at
least one interface, but some printers have several, in order to make them more flexible in a
multiplatform environment. If a printer has several interfaces, it can usually switch between
them on the fly so that several computers can print at the same time.
Communication Types
When I say communication types, I’m talking about the hardware technologies involved in
getting the information to and from the computer. There are seven major types:
Legacy Serial This is the traditional RS-232 serial port found on most PCs. The original
printer interface on the earliest computers, it has fallen out of favor and is seldom used
anymore for printing because it’s so slow.
Legacy Parallel Until recently, the parallel port on a PC was the overwhelming favorite
interface for connecting printers, to the point where the parallel port has become synonymous
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