Red Hat ENTERPRISE LINUX 4 - INTRODUCTION TO SYSTEM ADMINISTRATION Administration Manual

Also see for ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE: Installation guide Installation guide Tuning guide Installation guide Manual

Contents

Chapter 7. Printers and Printing 137Dot-matrix printers vary in print resolution and overall quality with either 9 or 24-pin printheads.The more pins per inch, the higher the print resolution. Most dot-matrix printers have a maximumresolution of around 240 dpi (dots per inch). While this resolution is not as high as those possible inlaser or inkjet printers, there is one distinct advantage to dot-matrix (or any form of impact) printing.Because the printhead must strike the surface of the paper with enough force to transfer ink from aribbon onto the page, it is ideal for environments that must produce carbon copies through the use ofspecial multi-part documents. These documents have carbon (or other pressure-sensitive material) onthe underside and create a mark on the sheet underneath when pressure is applied. Retailers and smallbusinesses often use carbon copies as receipts or bills of sale.7.2.2. Daisy-Wheel PrintersIf you have ever worked with a manual typewriter before, then you understand the technologicalconcept behind daisy-wheel printers. These printers have printheads composed of metallic or plasticwheels cut into petals. Each petal has the form of a letter (in capital and lower-case), number, orpunctuation mark on it. When the petal is struck against the printer ribbon, the resulting shape forcesink onto the paper. Daisy-wheel printers are loud and slow. They cannot print graphics, and cannotchange fonts unless the print wheel is physically replaced. With the advent of laser printers, daisy-wheel printers are generally not used in modern computing environments.7.2.3. Line PrintersAnother type of impact printer somewhat similar to the daisy-wheel is the line printer. However,instead of a print wheel, line printers have a mechanism that allows multiple characters to be simul-taneously printed on the same line. The mechanism may use a large spinning print drum or a loopedprint chain. As the drum or chain is rotated over the paper’s surface, electromechanical hammers be-hind the paper push the paper (along with a ribbon) onto the surface of the drum or chain, markingthe paper with the shape of the character on the drum or chain.Because of the nature of the print mechanism, line printers are much faster than dot-matrix or daisy-wheel printers. However, they tend to be quite loud, have limited multi-font capability, and oftenproduce lower print quality than more recent printing technologies.Because line printers are used for their speed, they use special tractor-fed paper with pre-punchedholes along each side. This arrangement makes continuous unattended high-speed printing possible,with stops only required when a box of paper runs out.7.2.4. Impact Printer ConsumablesOf all the printer types, impact printers have relatively low consumable costs. Ink ribbons and paperare the primary recurring costs for impact printers. Some Impact printers (usually line and dot-matrixprinters) require tractor-fed paper, which can increase the costs of operation somewhat.7.3. Inkjet PrintersAn Inkjet printer uses one of the most popular printing technologies today. The relatively low costand multi-purpose printing abilities make inkjet printers a good choice for small businesses and homeoffices.Inkjet printers use quick-drying, water-based inks and a printhead with a series of small nozzles thatspray ink onto the surface of the paper. The printhead assembly is driven by a belt-fed motor thatmoves the printhead across the paper.