Home > Articles

  • Print
  • + Share This
This chapter is from the book

Answers and Explanations

Objective 3.1

  1. c. If two devices are connected to the same IRQ line, a conflict occurs because it is not likely that the interrupt handler software can service both devices. The IRQ3 line works for both COM2 and COM4. When an external modem uses the COM2 port, no other device should use the COM4 port.

  2. c. In the case of a complete shutdown, or a significant sag, the best protection from losing programs and data is an uninterruptible power supply (UPS). A UPS is a battery-based system that monitors the incoming power and kicks in when unacceptable variations occur in the power source.

  3. b. The primary mission of the UPS is to keep the system running when a power failure occurs. Because it's battery based, it cannot keep the system running infinitely. For this reason, you should not connect nonessential, power-hungry peripheral devices such as a laser printer to the UPS supply.

  4. d. An uninterruptible power supply is an extremely good power-conditioning system. Because it always sits between the commercial power and the computer, it can supply a constant power supply to the system to protect it from spike damage.

  5. d. If a UPS is being used to keep a critical system in operation during the power outage, the high current drain of the laser printer would severely reduce the length of time that the UPS could keep the system running.

  6. d. Overvoltage conditions are classified as surges when their duration is measured in milliseconds or longer.

  7. a. Overvoltage conditions are classified as spikes when their duration is measured in nanoseconds or less.

  8. b. A surge suppressor protects the system from damages caused by minor power line interruptions. It passively filters the incoming power signal to smooth out variations.

  9. a. A cooling fan should be placed on any IC operating at clock speeds above 33MHz.

  10. d. Uninterruptible power supplies are battery-based systems that monitor the incoming power and kick in when unacceptable variations or outages occur in the power source.

  11. c. A surge suppressor is used to protect computer equipment from very small overvoltage occurrences by passively filtering the incoming power signal to smooth out variations.

  12. b. Sags, an undervoltage condition, can include voltage sags and brownouts. A voltage sag typically lasts only a few milliseconds, but a brownout can last for a protracted period of time. Sags can cause the system to suddenly reboot because it thinks the power has been turned off.

  13. a. A brownout is an undervoltage condition and can last for a protracted period of time, which makes it easy to spot.

  14. c. If a monitor is to be left on for an extended period of time with the same image on it, this can cause the image to become permanently "burned" into the phosphorous coating. To prevent this from occurring, install a screensaver package to constantly refresh the contents of the display.

  15. b. To recover from hardware failures, operator mistakes, and acts of nature, you should make system backups of the hard drive.

  16. a, b. (a) Copies of the system backup should be stored in a convenient but secure place. In the case of secure system backups, such as client/server networks, the backup copies should be stored where the network administrators can have access to them, but not the general public (for example, a locked file cabinet). (b) Many companies maintain a copy of their backup away from the main site. This is done for protection in case of disasters such as fire.

  17. c. If your trackball mouse responds erratically when you move it across the screen, the first thing you should do is clean the mouse. Use a lint-free swab to clean the X and Y trackball rollers inside the mouse.

  18. d. Because the CD-ROM stores data in the form of spots burned into an optical media, the RFI escaping from the monitor would not affect it. However, all of the other storage devices rely on magnetic storage that is susceptible to damage from RFI and other magnetic-field disturbances.

  19. c. The oxidation buildup occurring on electrical connectors and contacts reduces the flow of electricity through the connection. Even with proper handling, some corrosion can occur over time. This oxidation can be sanded off with emery cloth, rubbed off with a common pencil eraser or special solvent wipe, or dissolved with an electrical contact cleaner spray. The only acceptable answer offered in this question is the use of contact cleaner.

  20. d. High humidity can lead to heat-related problems and failures.

  21. a. The application of an antistatic spray or antistatic solution prevents the buildup of static charges on the components of the system. A solution composed of 10 parts water and 1 part common household fabric softener makes an effective and economical antistatic solution.

  22. d. A damp cloth is the best general-purpose cleaning tool for use with com-puter equipment, such as a monitor.

  23. b. With a trackball mouse, the trackball should be removed and cleaned periodically. Use a lint-free swab to clean the X and Y trackball rollers inside the mouse.

  24. d. Unlike the floppy disk drive, the mouse, and the printer, the keyboard's electronic circuitry is open to the atmosphere and should be vacuumed regularly. Dust buildup on the keyboard circuitry can cause its ICs to fail due to overheating.

  25. d. Manual cleaning of read/write (R/W) heads should be performed with isopropyl alcohol using a foam swab. Cotton swabs can shed fibers that can contaminate the drive and damage portions of its R/W head.

  26. a, b, d. Sources of heat buildup around the computer and its peripherals include direct sunlight from an outside window, locations of portable heaters in the winter, and papers and books piled up around the equipment.

  27. b. Copies of the system backup should be stored in a convenient but secure place. In the case of secure system backups, such as client/server networks, the backup copies should be stored where the network administrators can have access to them, but not the general public (for example, a locked file cabinet).

  28. d. High humidity can lead to heat-related problems.

  29. a. Microcomputers are designed to run at normal room temperatures. If the ambient temperature rises above about 85°F, heat buildup can become a problem.

  30. c. A static-free vacuum can be used to remove dust from inside cases and keyboards. Be sure to use a static-free vacuum because normal vacuums are, by their nature, static generators. The static-free vacuum has special grounding to remove the static buildup it generates.

  31. a, b. (a) The missing cover permits dust to accumulate in the system, forming the insulating blanket that traps heat next to active devices and can cause component overheating. (b) The missing slot cover interrupts the designed airflow patterns inside the case, causing components to overheat due to missing or inadequate airflow.

  32. b. As with any electronic device, computers are susceptible to failures caused by dust buildup, rough handling, and extremes in temperature.

  33. d. Oxidation can be removed from adapter card contacts with emery cloth, rubbed off with a common pencil eraser or special solvent wipe, or dissolved with an electrical-contact cleaner spray.

  34. d. To remove dust from the inside of computer cases, a small paintbrush is handy.

  35. a. The outer-surface cleaning should be followed by the application of an antistatic spray or antistatic solution to prevent the buildup of static charges on the components of the system.

  36. b. Outer-surface cleaning can be accomplished with a simple soap-and-water solution, followed by a clear water rinse. Care should be taken to make sure that none of the liquid splashes, or drips, into the inner parts of the system.

  37. a. Outer-surface cleaning can be accomplished with a simple soap-and-water solution, followed by a clear water rinse. Care should be taken to make sure that none of the liquid splashes, or drips, into the inner parts of the system. A damp cloth is easily the best general-purpose cleaning tool for use with computer equipment.

Objective 3.2

  1. a. Normal operating vibrations and temperature cycling can degrade the electrical connections between ICs and sockets over time. This gradual deterioration of electrical contact between chips and sockets is referred to as chip creep.

  2. c. A Class C fire extinguisher specified for use around electrical equipment should be on hand around computers.

  3. b. The surge suppressor's clamping speed rating describes how quickly it can react to changes in the incoming power level and act to minimize it.

  4. b. Proper grounding is the best defense against the disruptive effects of EMI.

  5. c. ESD is most likely to occur during periods of low humidity. If the relative humidity is below 50%, static charges can accumulate easily. ESD generally does not occur when the humidity is above 50%.

  6. b. To avoid damaging static-sensitive computer devices, ground yourself by touching the power supply housing with your finger before touching any components inside the system. This technique will only work safely if the power cord is attached to a grounded power outlet. The ground plug on a standard power cable is the best tool for overcoming ESD problems.

  7. c. Antistatic straps should never be worn while working on higher-voltage components, such as monitors and power supply units.

  8. a. Unlike ESD, which is the most damaging form of electrical interference associated with digital equipment and is destructive, the effects of EMI can be corrected without damage.

  9. c. Professional service technicians use grounding straps to minimize the chances of ESD during normal computer maintenance work involving MOS devices. These antistatic devices can be placed around the wrists or ankles to ground the technician to the system being worked on. These straps release any static present on the technician's body, and pass it harmlessly to ground potential.

  10. b. Normal operating vibrations and temperature cycling can degrade the electrical connections between ICs and sockets over time. This gradual deterioration of electrical contact between chips and sockets is referred to as chip creep. It is a good practice to reseat any socket-mounted devices when handling a printed circuit board.

  11. d. Of the possible choices provided, installing antistatic carpet is the only option that will help to minimize ESD.

  12. c. ESD is most likely to occur during periods of low humidity. If the relative humidity is below 50%, static charges can accumulate easily. Anytime the charge reaches about 10,000V, it is likely to discharge to grounded metal parts.

  13. d. 110V AC at 5 amps is much more dangerous than 25,000V DC at 5 microamperes according to the current-delivering capabilities (5 amps versus 5 microamperes) they create.

  14. c. The ampere-hour rating of the UPS describes how long it can supply power to a given size electrical load after a failure has occurred.

  15. c. Extremely high voltage levels (in excess of 25,000V) may be present inside the CRT housing, even up to a year after electrical power has been removed from the unit.

  16. d. Remove all power cords associated with the computer, and its peripherals, from the power outlet during thunder or lightning storms.

  17. b. Computer devices should be stored or transported in their original boxes using their original packing foam and protective storage bag because the contours in the packing foam of these devices are not compatible from model to model, or device to device. If the original boxes and packing materials are not available, make sure to use sturdy cartons and cushion the equipment well on all sides before shipping.

  18. a, b, c. When a disruption occurs, the UPS notifies the host computer so that its operating system can conduct an orderly shutdown of the system without losing data. The management software can also be configured to notify the system users to save and shut down, as well as to email or page an administrator to alert him to the failure.

  19. b. While touching only the insulated handle of the screwdriver, slide the blade of the screwdriver under the rubber cup of the anode and make contact with its metal connection. This should bleed off the high voltage charge to ground.

Objective 3.3

  1. c. Check your local waste management agency before disposing of them. Some landfills will not accept chemical solvents and cans. In this case, these items must be disposed of in a Subtitle-D dump site.

  2. c. Free liquids are those substances that can pass through a standard paint filter. If the liquid passes through the filter, it is free liquid and cannot be disposed of in the landfill.

  3. b. All hazardous materials are required to have Material Safety Data Sheets (MSDSs) that accompany them when they change hands. They are also required to be on hand in areas where hazardous materials are stored and commonly used.

  4. a, c. The MSDS contains information about what the material is, its hazardous ingredients, its physical properties, fire and explosion data, reactive data, spill or leak procedures, and any special protection or precaution information.

  5. d. Subtitle D dump sites are nonhazardous, solid-waste dump sites that can handle hardware components.

  6. b. Toner cartridges can be refilled and recycled. They can be very messy to refill and often do not function as well as new cartridges do. In many cases, the manufacturer of the product will have a policy of accepting spent cartridges.

  7. c. Local regulations concerning acceptable disposal methods for computer-related components should always be checked before disposing of any electronic equipment, such as a CRT.

  8. a. The desired method of battery disposal is recycling. It should not be too difficult to find a drop site that will handle recycling batteries and other hazardous materials.

  9. c. If the battery is expected to be stored for more than 30 days (as you would expect the replacement for a new computer to be) then you should fully discharge the battery and store it at normal room temperature.

  10. c. The best place to store computer equipment is in its original shipping box, surrounded by an antistatic bag wrapped in protective foam. The only correct version of this scenario in this question is the antistatic bag. Without this item, the other options are potentially harmful for digital equipment.

  11. b. Grounding is an important aspect of limiting electromagnetic interference (not to be confused with destructive ESD). Proper grounding routes induced EMI signals away from logic circuitry and toward ground potential where it is absorbed.

  • + Share This
  • 🔖 Save To Your Account