CompTIA A+ Certification Exam Objectives .. GDI graphics device interface. GHz gigahertz. GUI graphical user interface. GPS. The Windows GDI builds the page and then sends it to the printer. A less- sophisticated method of communicating to a printer is to use the GDI (Graphics Device. GDI is actually a Windows component and is not specific to printers. Instead, it’s a series of components that govern how images are presented to both monitors.
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Despite all of the talk about the “paperless office,”paper documents continue to be a vital part of the typical office. Some computers are even used exclusively for the purpose of producing paper documents. Many people simply still prefer dealing with a hard copy, even as portable devices have proliferated.
CompTIA A+ Certification Exam Guide, A+ Chapter 27 Print
Developers cater to this preference by using metaphors such as page, compti, and binder in their applications. In the past,your average office had an array of electronic and mechanical devices dedicated to performing a single task with paper documents. Think printers, copiers, scanners, and fax machines. Back in the s, the multifunction device MFDalso known as the multifunction printer MFPtried to consolidate multiple functions compptia printing and scanning into a single device.
At first these devices weren’t terribly great at any of their functions, but today’s mature multifunction devices are more common than their single-function counterparts. This chapter examines the common varieties of printers and scanners, then looks at specifics of how a laser printer works.
CompTIA A+ Certification Exam Guide, A+ Chapter 27 Printers and Multifunction Devices (1)
The chapter continues with the steps for installing a multifunction device in a typical personal computer, and concludes with troubleshooting issues. Because multifunction devices are so varied, we’ll take a look at some of the individual components and technologies you may find inside them separately be prepared to encounter these components as both standalone devices and included with other components in a multifunction device.
No other piece of your computer system is available in a wider range of styles, configurations, and feature sets than a printer, or at such a wide price variation. What a printer can and can’t do is largely comptiz by the type of printer technology it uses that is, how.
Modern printers can be categorized into several broad types: Printers that create an image on paper by physically striking an ink ribbon against the paper’s surface are known as impact printers. Although daisy-wheel printers essentially an electric typewriter attached to the computer instead of directly to a keyboard have largely disappeared, their cousins, dot-matrix printers, still soldier on in many offices. Although coomptia printers don’t deliver what most home users want high quality and flexibility at a low cost they’re still widely found in businesses for two reasons: Impact printers tend to be relatively slow and noisy, but when speed, flexibility, and print quality are not critical, they provide acceptable results.
Computers that print multipart forms, such as point of sale POS machines, use special impact paper that can print receipts in duplicate, triplicate, or more. Dot-matrix printers use a grid, or matrix, of copmtia pins, also known as print wires, to strike an inked printer ribbon and produce images on paper see Figure The case that holds the print wires is called a printhead. Using either 9 or 24 pins, dot-matrix printers treat conptia page as a picture broken up into a dot-based raster image.
The 9-pin dot-matrix printers are generically called draft quality, while the pin printers are known as letter quality or near letter quality NLQ. The BIOS for the printer either built into the printer or a printer driver interprets the raster image in the same way a monitor does, “painting” the image as individual dots. Naturally, the more pins, the higher the resolution. Figure illustrates the components common to dot-matrix printers.
Many dot-matrix printers use continuous-feed ggdi with holes on its sides that are engaged by metal sprockets to pull the paper through this is known as tractor-feed paper because the sprockets are reminiscent of the wheels on a tractor.
Some printers include this feature built-in,while others require a piece of additional hardware that flips the paper for the printer. The ink is ejected through tiny tubes.
Most inkjet printers use heat to move the ink, while a few use a mechanical method. The heat method printers use tiny resistors or electroconductive plates at the end of each tube that literally boil the ink; this creates a tiny air bubble that ejects a droplet of ink onto the paper, thus creating a portion of the image see Figure The ink is stored in special small containers called ink cartridges.
Older inkjet printers had two cartridges: The color cartridge had separate compartments comptiw cyan bluemagenta redand yellow ink, to print colors by using a method known as CMYK ccomptia read more about CMYK later in this chapter. If your color cartridge ran out of one of the colors,you had to purchase a whole new color cartridge or deal with a messy refill kit. Printer manufacturers began to separate the ink colors into three separate cartridges so that printers came with four cartridges: This not only was more cost-effective for the user, but it also resulted in higher quality printouts.
Today you can find color inkjet compttia with six, eight, or more color cartridges. In addition to the basic CMYK inks, the additional cartridges provide for green, blue, gray, light cyan, dark cyan, and more. Typically, printers using more ink cartridges produce higher quality printed images and cost more. The two key features of an inkjet printer are the print resolution-how densely the printer lays down ink on the page and the print speed. Resolution is measured in dots per inch dpi ; higher numbers mean that the ink dots on the page are closer together, so your printed documents will look better.
Resolution is most important when you’re printing complex images such as full-color photos, or when you’re printing for duplication and you care that your printouts look good. Print speed is measured in pages per minute ppmand this specification is normally indicated right on the printer’s box.
Most printers have one faster speed for monochrome printing that is, using only black ink and another for full-color printing. Another feature of inkjet printers is that they can support a staggering array of print media. Using an inkjet printer, you can print on a variety of matte or glossy photo papers, iron-on transfers, and other specialty media; some printers can print directly onto specially coated optical comptai, or even fabric.
The inks have improved over the years, too, now delivering better quality and longevity than ever. Where older inks would smudge if the paper got wet or start to fade after a short time, modern inks comptla smudge proof and of archival quality for example, some inks by Epson are projected to last up to years. Printer speed is a key determinant of a printer’s price, and this is an easy assertion to prove, so Try This!
Fire up your browser and head over to the Web site for Hewlett-Packard www. These five companies make most of the printers on the market today. Pick a particular printer technology and check the price, from the cheapest to the most expensive. Then look for printers that have the same resolution but different ppm rates. Check the prices and see how the ppm rate affects the price of two otherwise identical printers.
Smaller, specialized printers called snapshot printers use dye-sublimation specifically for printing photos at a reduced cost compared to their full-sized counterparts. The dye-sublimation printing technique is an example of the so-called CMYK cyan, magenta, yellow, black method of color printing. It uses a roll of heat-sensitive plastic film embedded with page-sized sections of cyan bluemagenta redand yellow dye; many also have a section of black dye.
A printhead containing thousands of heating elements, capable of precise temperature control, moves across the film, vaporizing the dyes and causing them to soak into specially coated xomptia underneath before cooling and reverting to a solid form. Figure shows how a dye-sublimation printer works. Dye-sublimation printers produce high-quality color output that rivals professional photo-lab processing. The first is the direct thermal. Direct thermal printers use a heating element to burn dots into the dgi of special heat-sensitive paper.
If you remember the first generation of fax machines, comptla already familiar with this type of printer. Many retail businesses still use it as a receipt printer, using large rolls of thermal paper housed in a feed assembly that automatically draws the paper past the heating element; some receipt printers can even cut the paper off the roll for you. Thermal wax printers work similarly to dye-sublimation printers, except that instead of using rolls of dye-embedded film, the film is coated with colored wax.
The thermal printhead passes over the ribbon and melts the wax onto the paper. Thermal wax printers don’t require special papers like dye-sublimation printers gddi, so they’re more flexible and somewhat cheaper to use, but their output isn’t quite as good because they use color dithering.
Using a process called electrophotographic imaging, laser printers produce high-quality and high-speed output of both text and graphics. Figure shows a typical laser printer. Laser printers rely on the photoconductive properties of certain organic compounds. Photoconductive means that particles gi these compounds, when exposed to light that’s the “photo” partwill conduct electricity.
Laser printers usually use lasers as a light source because of their precision. Some lower-cost printers use LED arrays instead. The first laser printers created only monochrome images; you can also buy a color laser printer, but most laser printers produced today are still gci. Although a color laser printer can produce complex full-color images such as photographs,they really shine for printing what’s known as spot color for example, eye-catching headings, lines, charts, or other graphical elements that dress up an otherwise plain printed presentation.
Toner Cartridge The toner cartridge in a laser printer is so named because of its most obvious activity: To reduce maintenance costs, however, many other laser printer parts, especially those that suffer the most wear and tear, have been incorporated into the toner gddi.
Although this makes replacement of individual parts nearly impossible, it greatly reduces the need for replacement; those parts that are most likely cmoptia break are replaced every time you replace the toner cartridge.
Imaging Drum The imaging drum ccomptia called the photosensitive drum is an aluminum cylinder coated with particles of photosensitive compounds. The drum itself is grounded to the power supply, but the coating is not. When light hits these particles, whatever electrical charge they may have “drains” out through the grounded cylinder.
Erase Lamp The erase lamp exposes the entire surface of the photosensitive drum to comptiw, making the photosensitive coating conductive. Any electrical charge present in the particles bleeds away into the grounded drum, leaving the surface particles electrically neutral.
When the primary corona or primary charge roller is charged with an extremely high voltage, an electric field or corona forms, enabling voltage to pass to the drum and charge the comptai particles on its surface. Laser The laser acts as the writing mechanism of the printer. Any particle on the drum struck by the laser becomes conductive and its charge is drained away into the grounded core of the drum.
The entire surface of the drum has a uniform negative charge of between and volts following its charging by the primary corona wire or charge roller. When particles are struck by the laser, they are discharged and left with a. Using the laser, we can “write” an image onto the drum. Note that the laser writes a positive image to the drum. Toner The toner in a laser printer is a fine compttia made up of plastic particles bonded to pigment particles. The toner cylinder charges the toner with a negative charge of between and compptia.
Because that charge falls between the original uniform negative charge of the photosensitive com;tia to volts and the charge of the particles on the drum’s surface hit by the laser voltsparticles of toner are attracted to the areas of the photosensitive drum that have been hit by the laser that is, areas that have a relatively more positive charge than the toner particles.
In older printers, the transfer corona, a thin wire, applied a positive charge to the paper, drawing the negatively charged toner particles to the paper. To prevent the paper from wrapping ocmptia the drum, a static charge eliminator removes the charge from the paper. It is also quite fragile-usually finer than a human hair.