Chapter 9.0


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Chapter 9.0

  1. 1. Chapter 9 Printers produce paper copies of electronic files. Scanners allow users to convert paper documents into electronic files. Common Printer Features Characteristics and Capabilities (i) Capabilities and Speed: The speed of a printer is measured in pages per minute (ppm). Speed is also affected by the complexity of the image and the quality desired by the user. (ii) Color or Black and White: a printer produces colors using subtractive mixing. The CMYK color model is a subtractive color model used in color printing. CMYK is the acronym for a color system composed by four colors, Cyan, Magenta, Yellow, and Black (represented by Key, as a base color). (iii) Quality: The quality of printing is measured in dots per inch (dpi). The larger the dpi number, the better the image resolution. When the resolution is higher, text and images are clearer. To produce the best high-resolution images, use high-quality ink or toner and high- quality paper. (iv) Reliability: A printer should be reliable. Because so many types of printers are on the market, research the specifications of several printers before selecting one. Wired Printer Connection Types To access a printer, a computer must have a compatible interface with the printer. The following are common interface types: (i) Serial Serial data transfer is the movement of single bits of information in a single cycle. • Serial ports are D-shell and are either male or female ports • The number of pins for each port may vary. Serial cables may have either a 9-pin connector or a 25-pin connector either end • The maximum length of a serial cable is 50 ft (15 m). A serial connection can be used for dot matrix printers because the printers do not require high-speed data transfer. (ii) Parallel • Parallel data transfer is faster than serial data transfer. • Parallel data transfer moves multiple bits of information in a single cycle. The data transfer path is wider than the serial data transfer path, allowing data to move more quickly to or from the printer. • IEEE 1284 is the current standard for parallel printer ports. Enhanced Parallel Port (EPP) and Enhanced Capabilities Port (ECP) are two modes that allow bi-directional communication. IEEE 1284 standard allows for cable length up to 30 ft (10 m). (iii) Small Computer System Interface (SCSI) pronounced “scuzzy”, uses parallel communication to achieve high data-transfer rates. Some types of SCSI are: • SCSI 1 - 50 pin connector • SCSI 2 (fast SCSI) - 50 pin connector • SCSI 2 (wide SCSI) - 68 pin connector • SCSI 3 (fast/wide SCSI) - 68 pin connector (iv) Universal Serial Bus (USB) is a common interface for printers and other devices. A USB printer cable is a four-wire cable that has two unique ends, labeled A and B. Rectangular A connector usually connects with the computer. Square-shaped B connector connects to the printer. (v) Firewire – Also known as i.LINK or IEEE 1394, is a high-speed, communication bus that is platform independent.
  2. 2. • Firewire connects devices such as printers, scanners, cameras • Allows a peripheral device to seamlessly plug into a computer • Devices are hot-swappable • A single plug-and-socket connection can attach up to 63 devices • Has a data transfer rate of up to 400 Mbps. (vi) Ethernet An interface for network printers. • Network printers are usually a resource shared on a network • Typically have high-speed output and options such as LAN fax, duplex, and finishers • Most have an RJ-45 interface for an Ethernet connection Types of Printers (1) Inkjet Printers Inkjet printers produce high quality prints. Inkjet printers are easy to use and inexpensive compared to laser printers. There are two types of inkjet nozzles: • Thermal - A pulse of electrical current is applied to heating chambers around the nozzles. The heat creates a bubble of steam in the chamber which forces ink out through the nozzle. • Piezoelectric crystals are located in the ink reservoir at the back of each nozzle. A charge is applied to the crystal causing it to vibrate. This vibration of the crystal controls the flow of ink onto the paper. Inkjet Printer Components Inkjet printers use ink cartridges that spray ink onto a page through tiny holes. The tiny holes are called nozzles and are located in the print head. The print head and ink cartridges are located on the carriage, which is attached to a belt and motor. As rollers pull paper in from the feeder, the belt moves the carriage back and forth along the paper as the ink is sprayed in a pattern on the page. Inkjet printers use plain paper to make economical prints. Special-purpose paper may be used to create high-quality prints of photographs. Print quality of an inkjet printer is measured in dots per inch (dpi). A higher dpi rating provides greater image detail. Advantages of an inkjet printer: Initial low cost High resolution Quick to warm up Disadvantages of an inkjet printer: Nozzles are prone to clogging. Ink cartridges are expensive. Ink is wet after printing. (2) Laser printers A laser printer is a high-quality, fast printer that uses a laser beam to create an image. The central part of the laser printer is its electrophotographic drum. When laser light strikes the drum, it becomes a conductor at the point where the light strikes. The laser beam draws an electrostatic image on the drum. The undeveloped image is passed by a supply of dry ink or toner that is attracted to it. The drum turns and brings this image in
  3. 3. contact with the paper, which attracts the toner from the drum. A fuser melts the toner into the paper. The Seven main components contained within a laser printer: • Toner cartridge • Laser scanner • High-voltage power supply • Paper transport mechanism • Transfer corona • Fuser assembly • Control circuitry • Ozone filter Laser Printing Process: 1. Processing - The data from the source must be converted into a printable form. The printer converts data from common languages, such as Adobe PostScript (PS) or HP Printer Command Language (PCL), to a bitmap image stored in the printer’s memory. Some laser printers have built in Graphical Device Interface (GDI) support. GDI is used by Windows applications to display printed images on a monitor so there is no need to convert the output to another format such as PostScript or PCL. 2. Charging - The previous latent image on the drum is removed and the drum is conditioned for the new latent image. A wire, grid, or roller receives a charge of approximately -600 volts DC uniformly across the surface of the drum. The charged wire or grid is called the primary corona. The roller is called a conditioning roller. 3. Exposing - To write the image, the photosensitive drum is exposed with the laser beam. Every portion of the drum that is scanned with the light has the surface charge reduced to about -100 volts DC. This electrical charge has a lower negative charge than the remainder of the drum. As the drum turns, an invisible latent image is created on the drum. 4. Developing - The toner is applied to the latent image on the drum. The toner is a negatively charged combination of plastic and metal particles. A control blade holds the toner at a microscopic distance from the drum. The toner then moves from the control blade to the more positively charged latent image on the drum. 5. Transferring - The toner attached to the latent image is transferred to the paper. A corona wire places a positive charge on the paper. Because the drum was charged negatively, the toner on the drum is attracted to the paper. The image is now on the paper and is held in place by the positive charge. Because color printers have three cartridges of ink, a colored image must go through multiple transfers to be complete. To ensure precise images, some color printers write multiple times onto a transfer belt that transfers the complete image to paper. 6. Fusing - The toner is permanently fused to the paper. The printing paper is rolled between a heated roller and a pressure roller. As the paper moves through the rollers, the loose toner is melted and fused with the fibers in the paper. The paper is then moved to the output tray as a printed page. Laser printers with duplex assemblies can print on both sides of a sheet of paper. 7. Cleaning - When an image has been deposited on the paper and the drum has separated from the paper, the remaining toner must be removed from the drum. A printer might have a blade that scrapes the excess toner. Some printers use an AC voltage on a wire that removes the charge from the drum surface and allows the excess toner to fall away from the drum. The excess toner is stored in a used toner container that is either emptied or discarded.
  4. 4. Advantages of a laser printer: Low cost per page High ppm High capacity Prints are dry Disadvantages of a laser printer: High cost of start up Toner cartridges are expensive Require a high level of maintenance (3) Thermal Printers Some retail cash registers or older fax machines might contain thermal printers. Thermal paper is chemically treated and has a waxy quality. Thermal paper becomes black when heated. After a roll of thermal paper is loaded, the feed assembly moves the paper through the printer. Electrical current is sent to the heating element in the print head to generate heat. The heated areas of the print head make the pattern on the paper. A thermal printer has the following advantages: Longer life because there are few moving parts Quiet operation No cost for ink or toner A thermal printer has the following disadvantages: Paper is expensive. Paper has a short shelf life. Images are poor quality. Paper must be stored at room temperature. Color printing is not available. (4) Impact printers Impact printers have print heads that strike an inked ribbon, causing characters to be imprinted on the paper. Dot matrix and daisy wheel are examples of impact printers. The following are some advantages of an impact printer: Uses less expensive ink than inkjet or laser printers Uses continuous feed paper Has carbon-copy printing ability The following are some disadvantages of an impact printer: Noisy Low-resolution graphics Limited color capability Types of Impact Printers Daisy-wheel printer - The wheel contains the embossed letters, numbers, and special characters. Wheel is rotated until the required character is in place, and an electromechanical hammer pushes the character into the ink ribbon and against the paper. Dot-matrix printer - Print head contains pins that are surrounded by electromagnets. When the electromagnets are energized, the pins push forward onto the ink ribbon in patterns, forming a character. The number of pins on a print head, 9 or 24, indicates the quality of the print. The highest quality of print that is produced by the dot matrix printer is referred to as near letter quality (NLQ). Most dot-matrix printers use continuous feed paper with perforations between each sheet. 1. Which factor affects the speed of an inkjet printer?
  5. 5. the desired quality of the image the size of printer power supply the quality of the paper the cost of the inkjet cartridges 2. What are two cables that are used to connect a computer to a printer? (Choose two.) serial FireWire PS/2 HDMI eSATA 3. What is a characteristic of thermal inkjet nozzles? The heat creates a bubble of steam in the chamber. Heat is applied to the ink reservoir of each nozzle. The vibration of the crystal controls the flow of ink. A charge is applied to the printhead. 4. In laser printing, what is the name of the process of applying toner to the latent image on the drum? developing charging transferring fusing 5. What is the purpose of the Additional Drivers button in the Sharing tab of the Printer Properties? to add additional drivers for other operating systems to add additional drivers for other printers in the network to add additional drivers for duplex printing to add additional drivers for other printers connected to the computer 6. A small LAN uses a shared printer that is connected to a computer. None of the users can print but all of the users can access the shared resources on the computer to which the printer is locally connected. What is a possible cause of this? The cable that connects the printer to the PC is faulty. The printer needs a new ribbon. The printer spool is full. The printer has the wrong paper loaded.
  6. 6. 7. How would a user install a new USB printer on a PC that is running Windows 7 Professional? Connect the printer and power it on. Windows will detect the printer and install the needed drivers. Copy the printer driver to the System32 folder. Click Start > All programs > Control Panel > Printers and Faxes > right-click on the desired printer and choose Add. Configure the BIOS to accept the specific model of printer in the USB port. 8. A Windows 7 computer has several printers configured in the Control Panel Devices and Printers window. Which printer will the computer choose to be the first option for printing? the printer that is set as the default printer the software-based printer that is used to create PDF files the software-based printer that is used to create XPS files a manual selection, which is always needed 9. What are two methods to share a printer wirelessly? (Choose two.) IEEE 802.11 standards infrared WiMax satellite microwave 10. A user discovers that an inkjet color printer is printing different colors from those that are shown on the screen. What can be done to solve this problem? Calibrate the printer. Adjust the printer spool. Replace the fuser. Replace the drum. 11. The users on a LAN are reporting that computers respond slowly whenever high resolution photographs are being printed on the color laser printer. What would be the cause of this problem? The printer does not have enough memory to buffer an entire photograph. The printer is not configured for duplex printing. The paper is not adequate for photograph printing. The printer is not configured for the proper paper orientation.
  7. 7. 12. What is a characteristic of global and per-document options in print settings? Per-document options override global options. Global options take precedence over per-document options. It is not possible to configure per-document options. It is not possible to configure global options. 13. What is true about the PostScript language? It handles complex printing jobs. It prints faster than other languages do. It requires less printer memory than other languages require. It allows the page to be rendered in the local workstation. 14. What are two closed-ended questions that a technician could ask a user while trying to identify the problem with a printer? (Choose two.) Is the printer powered on? Can you print a test page on the printer? What were you doing when the problem occurred? What error messages were displayed when the problem occurred? What recent software or hardware changes have been made to your computer? 15. After applying a solution to a printer problem, a technician restarts the printer and prints a test page. Which step of the troubleshooting process is the technician applying? verifying the solution and system functionality identifying the problem testing a theory to determine the cause of the problem documenting findings, actions, and outcomes 16. A user notices that a job submitted to a printer is displayed in the print queue, but the printer is not printing the document. What is a probable cause of this problem? a bad cable connection an incorrect printer driver the wrong paper type a printer spooler not installed 17. A technician recorded that a new fuser roller unit was installed in a laser printer to
  8. 8. solve a printing problem. Which step in the troubleshooting process did the technician just perform? documenting findings, actions, and outcomes verifying the solution and system functionality identifying the problem testing a theory to determine the cause of the problem 18. Where would network printer sharing be configured in a Windows 7 environment? Network and Sharing Center Devices and printers Printers and Other Hardware Ease of Access Center 19. What are two functions of a print server? (Choose two.) provide print resources to all connected client computers store print jobs in a queue until the printer is ready ensure that the connected client computers have up-to-date printer drivers store backups of documents sent to the printer provide uninterrupted power to the printer 20. Which action supports an effective printer preventive maintenance program? Reset the printer page counters if available. Replace laser printer toner at set predetermined time intervals. Clean inkjet print heads when they stop working. Disconnect the printer from the power source when it is not in use. 21. Which two replacement parts are typically found in a laser printer maintenance kit? (Choose two.) fuser assembly transfer rollers toner cartridge pack of paper replacement print head 22. How can the life of a thermal printer be extended?
  9. 9. Clean the heating element regularly with isopropyl alcohol. Clean the inside of the printer with a vacuum cleaner with a HEPA filter. Keep the paper dry in a low humidity environment. Wipe the outside of the printer with a damp cloth.