Laptop locks (see Figure 3-19) use a combination or keyed lock, and are designed to lock the lap-top (or other secured device) to a fixed location such as a table.
Figure 3-19 A combination laptop security lock.
Chapter 4
Printers
There are many kinds of printers. The A+ exams focus on a few common ones: laser, inkjet, thermal, and impact (dot matrix). The following is a list of common printer measurements:
Pages per minute (PPM) —Measures printer speed.
Characters per second (CPS) —Measures printer speed in impact (dot-matrix) printers. Dots per inch (DPI) —Measures quality (resolution).
Mean time between failures (MTBF) —Measures reliability.
Cost per page (CPP) —Measures the price of each printed page. A proper measurement ofCPP takes into consideration the cost of ink, paper, electricity, and scheduled printer mainte-nance.
Laser
Monochrome laser printers prorvide a good balance between cost and quality. They are quiet, reliable, and produce high-quality printouts at a very low cost per page (CPP). Table 4-1 outlines the seven steps of the laser-printing process with a helpful mnemonic.
Compared to discussions of the EP process in earlier versions of CompTIA A+ Certification exams, the exams now recognize the role of processing in laser printing, and have renamed some of the steps and changed the starting and ending point of the process. Use the new terms and sequence listed in this chapter as you prepare for the exams.
Table 4-1 Laser-Printing Process
| Step | Details of Each Step | Mnemonic | |
| 1. | Processing | The printer receives page, font, text, and graph- | Proper |
| ics data from the printer driver and creates a page | |||
| image. | |||
| 2. | Conditioning | Puts uniform charge of –600 VDC. This phase is | Californian |
| also called charging. | |||
| 3. | Exposing (formerly | Laser traces the image on the charged drum and | Elephants |
| referred to as Writing) | changes the voltage to –100 VDC in those areas | ||
| the laser touched. | |||
| 4. | Developing | Negatively charged toner is applied to the drum | Dance |
| and sticks to the areas with altered voltage. | |||
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Table 4-1 Continued
| Step | Details of Each Step | Mnemonic | |
| 5. | Transferring | The secondary corona wire or roller charges the | The |
| paper. The toner is statically attracted to the paper. | |||
| 6. | Fusing | Rollers melt the toner and embed it into the paper. | Fandango |
| 7. | Cleaning | The drum is cleaned by a wiper or in some cases | Cleverly |
| an electrical charge can drop excess toner from | |||
| the drum. | |||
Some all-in-one (multifunction) printer/scanner/copier devices use laser-printer engines and are configured for printing the same way as a printer is.
Figure 4-1 provides an “inside” view of a typical monochrome laser printer and its components.
Paper feed direction
Paper path
| Fold-down | |
| output tray |
2 3 
5 
6 
Pickup rollers
Figure 4-1 A typical monochrome laser printer’s components.
A color laser printer works in a somewhat similar fashion, but uses four toner cartridges and a transfer belt to transfer toner (see Figure 4-2).
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| Paper path | Cleaning |
| unit | |
| Fusing rollers | Waste toner |
Toner particles
OPC Belt
| Transfer | ||||||
| roller | ||||||
| Imaging drum | Erase lamp | Laser | ||||
| Paper pickup | Cleaning | Charger | Laser mirror | |||
| blade | ||||||
| Paper in paper tray | ||||||
Figure 4-2 A typical color laser printer’s components.
Keep in mind that laser printers are page printers; the entire page must fit into the printer’s mem-ory. Laser printers can use page-compression techniques to help complex pages (graphics, many fonts) to fit into the printer’s memory, but if printing a page produces an error, you can typically reduce the resolution of graphics on the page through the printer properties sheet’s Advanced Options dialog (see Figure 4-3).
Figure 4-3 Reducing graphics resolution to enable a complex page to print.
84 CompTIA A+ Quick Reference
Inkjet
Inkjet printers include either thermal or piezoelectric nozzles:
Thermal nozzles boil the ink and jets of steamed ink shoot onto the paper. Thermal inkjet printers’ ink cartridges also include the print head.
Piezoelectric nozzles energize crystals that vibrate and control ink flow. Piezoelectric noz-zles are built in to the printer and the ink cartridges snap into the built-in print heads.
Both types of inkjet printers use at least four ink colors: Cyan, Magenta, Yellow, and blacK (hence the initials CMYK for this color model). Some printers optimized for photo printing add additional color inks or might have interchangeable blank inks for text and black-and-white photo printing.
The inkjet print process is as follows:
1. A feed mechanism loads paper into the printer by means of a roller.
2. The print head moves into position by means of a carriage bar across the width of the paper and a belt that moves the print head along the carriage.
3. Under command from the printer driver, ink is deposited on the paper to create letters and shapes as the paper is moved through the printer.
4. If the printer contains a duplexer and the print job calls for two-sided printing, the paper is reversed and the print job continues on the reverse side.
5. The paper is ejected.
Figure 4-4 shows typical components of an inkjet printer optimized for photo and text printing.
Because a printed line or shape might require several passes of the print head, it is important to properly align the print head. Some printers perform this task automatically when the ink cartridg-es are replaced, whereas others can perform this task on demand.
To deal with clogged inkjet nozzles, it is sometimes necessary to run a self-cleaning utility. Both the alignment and the self-cleaning utilities are usually found in menus in the printer properties sheet. Figure 4-5 illustrates a typical maintenance menu with these and other options.
Most all-in-one (multifunction) printer/scanner/copier devices use inkjet printer engines and are configured for printing the same way as a printer is.
Chapter 4: Printers 85
1. Dust cover
2. LCD instruction panel
3. Control panel
4. Printhead drive belt
5. Output tray
6. Ink cartridges
7. Flash memory card reader
Figure 4-4 A typical inkjet printer with its cover open.
Figure 4-5 This printer’s maintenance menu offers options for print head cleaning, alignment, andchecking ink levels.
86 CompTIA A+ Quick Reference
Thermal
Thermal printers are used most often on point-of-sale systems to print receipts and other inex-pensive continuous feed outputs, such as those produced by EKGs, label makers, and old fax machines. Most thermal-print paper is roll paper, but a few portable printers for PCs use sheet-fed thermal paper. The print process works like this:
1. A feed mechanism loads paper into the printer.
2. The heating element heats the paper to form letters and shapes.
3. The paper is ejected.
Some older printers use a thermal-transfer method that uses plain paper and thermal ribbons to print. In this variation, the printer uses a print head and a ribbon instead of a full-width heating element.
Figure 4-6 illustrates direct-thermal and thermal-transfer printing technologies.
| Printed areas on media | Thermal printhead | ||||
| Heat-sensitive media | |||||
Wax/resin
Ribbon transfer material
Wax/resin transfer material transferred to media surface
Media
Figure 4-6 Direct-thermal (top) and thermal-transfer (bottom) printing technologies.
Impact Printer
Impact printers are primarily used for reporting, warehousing, and some types of point-of-sale use today. The print process for a dot-matrix printer (its rival, the daisy-wheel printer, is long obsolete) works this way:
Chapter 4: Printers 87
1. A tractor-feed mechanism pulls (or pushes) paper into place from the rear or bottom of the printer. Some printers can use single sheets of paper, but this usage is rare today.
2. A carriage and band mechanism is used to position the print head.
3. A series of fine wires in the print head (9-pin, 18-pin, and 24-pin) are fired by a solenoid to create letters and shapes that are transferred by a printer ribbon to the paper.
4. The feed mechanism pulls the paper through until it can be torn off.
Impact printers are measured in CPS, not PPM. Near letter quality (NLQ) is the best quality a dot-matrix printer can have. Impact printers can use carbon copy paper because the impact travels through to the carbon copies beneath the original paper.
Figure 4-7 illustrates a typical wide-carriage dot-matrix impact printer.
1. Rear cover (top cover removed, not shown)
2. Paper supports for tractor-feed paper path
3. Platen for using single sheets of paper
4. Manual paper advance knob
5. Paper bail lifter
6. Paper bail
7. Timing/drive belt
8. Printhead signal control cable
9. Printhead with heat sink
10. Ribbon holder
11. Printhead support rod
12. Head gap adjustment
13. Tractor/friction-feed selector lever
14. Tractor feed
Figure 4-7 Components of a typical dot-matrix impact printer; although this example is a wide-carriage model, printers that use standard-width paper are similar.
