Study Unit - External I-O Devices and Printers

Study Unit

External I/O Devicesand PrintersReviewed By

Brandon Nolta

About the Reviewer

Brandon Nolta has more than a decade of experience in information

technology, system administration, software testing, technical

documentation, and freelance writing. He has worked for several

companies in various technical capacities, including Hewlett-Packard

and MPC. His freelance experience includes working as an Internet

researcher for the Sci-Fi Channel (now SyFy).

Mr. Nolta has a bachelor’s degree in mathematics from the

University of Idaho and a master’s degree in English from Boise

State University. He holds several technology-related certifications,

including A+, Network+, and Microsoft Certified System Adminis-

trator (MCSA).

Copyright © 2011 by Penn Foster, Inc.

All rights reserved. No part of the material protected by this copyright may bereproduced or utilized in any form or by any means, electronic or mechanical,including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the copyright owner.

Requests for permission to make copies of any part of the work should be mailed to Copyright Permissions, Penn Foster, 925 Oak Street, Scranton,Pennsylvania 18515.

Printed in the United States of America

All terms mentioned in this text that are known to be trademarks or service marks have been appropriately capitalized. Use of a term in this text should not beregarded as affecting the validity of any trademark or service mark.

The personal computer (PC) that you’ve been working with

consists of more than just a system board and some expan-

sion cards contained in the system case. You should think of

the PC as a “system” that incorporates many different types

of components and devices with different functions. As a PC

repair technician, you’ll be called upon to support entire PC

systems including monitors, keyboards, and printers.

This study unit identifies and describes the typical I/O

(input/output) devices you’ll encounter in supporting a

computer system. It also discusses the interconnections

required to connect I/O devices to your PC and explains how

the operating system communicates with these devices.

iii

Previe

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When you complete this study unit, you’ll beable to

• Describe the system resources used to supportinput/output devices

• Install a new device on a personal computer

• Resolve resource conflicts

• Describe the cabling and connection options whenadding a new device

• Identify and evaluate I/O devices

• Explain how printers work

• Support, troubleshoot, and repair printers

• Install a printer on a PC or on a local area network(LAN)

Remember to regularly check “My Courses” on your student homepage.

Your instructor may post additional resources that you can access to

enhance your learning experience.

ATTACHING I/O DEVICES 1Fundamentals of Peripheral Installations 1Embedded BIOS on Devices 2Device Drivers 2Application Software 5Ports and Expansion Slots 5Using PCI Expansion Slots 6When Device Installations Create Problems 8Using Serial Ports 8Using Parallel Ports 10SCSI Devices 10Using USB Ports 12Using FireWire/iLink Ports 14

EXTERNAL I/O DEVICES 17Keyboards 17Pointing Devices 17Monitors 20Video Cards 22Modems 24Installing Devices Using Windows 7 25Plug-and-Play Devices 27Hot-Pluggable Devices 29USB Devices 29Other Add-on Devices 34

PRINTERS 42Laser Printers 42Color Laser Printers 44Color Ink-Jet Printers 46Color Management 47Sharing Printers 50Products for Network Printers 51Practical Exercise 51

SELF-CHECK ANSWERS 55

v

Contents

Contents

1

ATTACHING I/O DEVICESVarious system resources are needed to install and support

external devices. In the following sections, we’ll explain how

the operating system communicates with devices. You’ll learn

how to install a new device on a PC and how to resolve con-

flicts that are caused when two devices request the same

system resources. In addition to the standard legacy system

ports, you’ll also learn about USB and FireWire/iLink ports,

which allow a variety of devices to be easily connected to

your PC.

Fundamentals of PeripheralInstallationsAdded peripherals need a device driver or BIOS system

resources, which may include an interrupt request number

(IRQ), direct memory access channel (DMA channel), input/

output addresses (I/O addresses), upper memory addresses,

and application software.

Software has many different levels, including device drivers

that interface with the hardware and application software

that interfaces with the drivers.

When several peripheral devices are added to a system, they

might try to use the same resources, which could cause

peripherals not to work. When two devices try to use the

same IRQ, DMA channel, I/O address, or upper memory

addresses, it usually causes problems.

External I/O Devices and Printers

External I/O Devices and Printers2

Some peripherals are internal, meaning that they’re installed

inside the computer case. Internal peripherals include optical

drives and Zip drives, along with cards to support audio,

video, and communications. External peripherals include

printers, plotters, scanners, projectors, cameras, building

environmental controls, lighting, security systems, and a host

of others.

There are three basic steps for adding peripherals to a PC: (1)

plug in the device, (2) install drivers, and (3) install application

software.

Embedded BIOS on DevicesSome peripheral devices require several levels of software.

Some external devices store needed software in their own

cabinet, on a ROM chip, or a ROM chip on the interface board.

This is called firmware or BIOS. Some peripheral devices

designed for use on a wide variety of systems contain RAM for

temporary storage of data. The technique varies with devices

and can include flipping DIP switches, moving jumpers, and

in most cases, using programs provided by the device manu-

facturer. Rarely, it’s necessary during installation to interface

with the BIOS to set an IRQ number or I/O addresses.

In some cases, system BIOS as well as device BIOS may

come into play. BIOS on the hard drive manages access to

the hard drive, while system BIOS on the system board man-

ages communication between the hard-drive BIOS and the

operating system (OS).

Device DriversPeripherals require device drivers. The two common types

of drivers since Windows Vista was released are 32-bit and

64-bit. Windows uses 32-bit drivers natively, unless you’re

using a 64-bit version of Windows.

External I/O Devices and Printers 3

Windows 32-Bit and 64-Bit Drivers

Unlike previous versions, Windows XP and later doesn’t need

to load drivers in specific startup files, because all common

drivers are preloaded in the operating system. Booting the

system with the device plugged in tells Windows to activate

the driver. Windows drivers can be activated when a device is

used and deactivated when not used to conserve memory.

Most extra Windows drivers come as part of a hardware

package on a CD when you purchase a device. Windows and

some device manufacturers offer the latest revisions to drivers

on their Web sites. Windows allows you to view and change

device drivers from the Control Panel. In Windows 7, for

example, click on Start, then Control Panel. Then click on

Display and click Adjust Resolution to view the currently

installed display driver, as shown in Figure 1.

To change the driver, click on Advanced Settings, the

Adapter tab, the Properties button, the Driver tab, and then

the Update Driver button. The Update Device Driver Wizard

will appear, as shown in Figure 2.

You can search manually for supported drivers or let Windows

search for you. If you have a driver from a device that’s not

supported by Windows, perform the search manually by

FIGURE 1—CurrentlyInstalled Display Driver


selecting Browse my computer for driver software. Click

Let me pick from a list to be able to add the driver from a

CD, DVD, or a downloaded folder on the hard drive, as

shown in Figures 3 and 4.

FIGURE 2—UpdateDevice Driver WizardDialog Box

FIGURE 3—Update DeviceDriver Wizard Installation


Always use 32-bit drivers with 32-bit Windows systems and

64-bit drivers with 64-bit Windows systems. While 64-bit

Windows versions can use 32-bit drivers, performance will

decrease.

Application SoftwareMost devices include basic application software so they can

be used as soon as they’re installed. For example, a scanner

will usually include software to scan and manipulate images

and documents. Advanced application software can be pur-

chased to replace the basic software included with the device

and provide more function.

Ports and Expansion SlotsThere are several ways that devices can connect to a PC. The

following is a preview of the topics we’ll discuss for connect-

ing devices to your computer.

Most computers come with serial, parallel, USB, and some-

times FireWire/iLink ports mounted on the system board. On

older systems, an I/O controller card in an expansion slot

provided serial and parallel ports.

FIGURE 4—Choose thedriver you want to use.


Using PCI Expansion SlotsPCI and PCI-Express are local buses that run in sync with

the CPU. PCI-Express slots are often colored yellow so they

can be easily distinguished from the PCI expansion slots,

which are usually white or green. Figure 5 shows the PCI-

Express X16 and X1 slots on a system board for comparison.

Because the PCI-Express bus is faster than the PCI bus, PCI-

Express slots are often used for fast I/O devices such as

network cards or graphics adapters. When installing either a

PCI or PCI-Express card, it’s unlikely you’ll need to configure

the IRQ or I/O address because the startup PnP BIOS and

onboard bus controller do this for you.

Use the Device Manager to see which IRQ has been assigned

to a PCI device. Go to Settings and click on Control Panel.

Click on the System icon to bring up the System Properties

window. Select the Device Manager link. Now, suppose your

PC has a PCI video card. Clicking the c next to “Display

adapters” will yield the name of this video card. Double-click

on the device to bring up its Resources window; here you can

find which IRQ (09, 10, 11) has been assigned to the device.

PCI-Express Slots PCI (Peripheral Component Interface) and PCI-Express expansion slots on

the system board allow insertion of expansion cards to attach devices to

the PCI and PCI-Express buses.

Serial Port A male communication port on a computer used for transmitting data seri-

ally, one bit at a time. Serial ports are often called COM1, COM2, COM3,

etc., and use DB-9 or DB-25 connectors.

Parallel port A female communication port on a computer used for transmitting data in

parallel, eight bits at a time. Ports are labeled LPT1 and LPT2.

SCSI SCSI (usually pronounced scuzzy) stands for “Small Computer System

Interface.” SCSI adapters can have many different standards that need to

be taken into consideration when matching the host adapter and the con-

nected devices.

USB The Universal Serial Bus is standard on newer computers. It attaches a

wide range of devices and is easier to use than serial and parallel ports.

FireWire/iLink A high-speed serial bus often used to connect real-time data devices such

as audio/visual equipment to a PC. Also known as IEEE 1394 (Institute of

Electrical and Electronic Engineers).


PCI Bus IRQ Steering

Starting with PCI 2.1, PCI and PCI-Express both utilize PCI

bus IRQ steering, making it possible for PCI devices to share

an IRQ. By using PCI bus IRQ steering, Windows can auto-

matically assign or “steer” the PCI bus’ IRQs. All versions of

Windows from XP forward support IRQ steering.

Sometimes an IRQ conflict can happen when the startup

BIOS isn’t aware that a legacy device is using a particular

IRQ and assigns that IRQ to the PCI or PCI-Express bus,

which then assigns it to a specific device. With IRQ steering,

Windows can sometimes solve the problem by reassigning

another IRQ to the bus to allow the legacy device to be the

sole owner of its IRQ.

For this to happen, Windows must detect an unused IRQ and

assign it as a substitution. It then reserves this IRQ for PCI

or PCI-Express use. The word “Holder” indicates an IRQ is

reserved.

IRQ steering can also cause a problem. If Windows puts a

holder on an IRQ, this might cause the device using it to

have problems. Also, if two devices are having conflicts,

CaseBack

CaseFront

PCI–Express x16

PCI–Express x1

AGP

PCI

FIGURE 5—PCI-ExpressSlots


sometimes IRQ steering can mask the problem, making it dif-

ficult to diagnose. IRQ steering can erroneously put a holder

on an IRQ that’s being used by a legacy device.

When Device Installations Create ProblemsSuppose you install a new sound card and it doesn’t work.

You also notice your network card has stopped communicat-

ing. Poor cable or card connections can cause these symptoms.

Check all connections, then remove the sound card and see if

the network card starts working again.

Device documentation is the best place to begin diagnosing

device installation problems.

Using Serial PortsSerial ports are always male ports on the computer and use

DB-9 or DB-25 connectors. DB stands for data bus, and the

number 9 or 25 indicates the number of pins (Figure 6).

25–Pin Female Parallel Port

9–Pin Male Serial Port 15–Pin Female Game Port

FIGURE 6—Serial, Parallel, and Game Ports


Designers designated COM1, COM2, COM3, and COM4 as

serial ports to simplify allocation of system resources. COM

assignments represent a designated IRQ and I/O address, as

shown in Table 1.

Serial ports are physical connections. COM assignments are

logical connections. Saying COM1 is the same thing as saying

IRQ4 and I/O address 03F8.

Configuring an I/O card with a serial port COM assignment

usually requires the arrangement of jumpers on the card.

CMOS is most often used for COM assignments of ports con-

nected directly to the system board. Sometimes the setup

screen shows COM assignments, and sometimes it shows the

IRQ and I/O address.

A serial port conforms to the standard interface called

RS-232 (Reference Standard 232). Sometimes written

RS-232b or RS-232c, the lower-case “b” or “c” represents

the revision level. Even though serial ports are available in 9-

and 25-pin configurations, only nine of the pins are used.

Adapters are available on the market to convert the ports to

suit whatever serial cables you happen to be using.

Table 2

STANDARD DEFAULT PORT ASSIGNMENTS

Port IRQ I/O Address in Hex Type

COM1 IRQ4 03F8-03FF Serial

COM2 IRQ3 02F8-02FF Serial

COM3 IRQ4 03E8-03EF Serial

COM4 IRQ3 02E8-02EF Serial

LPT1 IRQ7 0378-037F Parallel

LPT2 IRQ5 0278-027F Parallel

1


Using Parallel PortsTypically, there are three types of printer ports:

• SPP—Standard parallel port

• EPP—Enhanced parallel port

• ECP—Extended-capabilities parallel port

The SPP is often referred to as a Centronics port or normal

parallel port. The name “Centronics” is taken from the 36-pin

connection used for printers (Figure 7). A standard parallel

port allows data flow in only one direction.

The EPP and ECP are both bidirectional.

The extended-capabilities parallel port

uses Direct Memory Access (DMA).

Cable length can be critical in parallel port

connections. Ten feet is normally satisfac-

tory, but you should never exceed fifteen

feet.

When configuring parallel ports it’s impor-

tant to read the documentation provided

with the I/O card. If the port is connected

directly to the system board, look at CMOS

setup to configure the port.

SCSI DevicesInstalling a SCSI device is normally done one of two ways:

1. Install the SCSI device using a simplified version of a

SCSI host adapter designed to accommodate one or two

devices. These adapters often come bundled in the SCSI

device package.

2. Install the SCSI device on an existing or new host

adapter designed to handle several devices.

DB 25–PinConnection

36–PinCentronicsConnection

(Printer)

FIGURE 7—Standard Parallel Printer Cable


Matching the Host Adapter to SCSI Devices

When matching a host adapter or determining if an existing

host adapter will work with a new SCSI device, consider the

following:

• Legacy SCSI standards include SCSI-1, SCSI-2, SCSI-3,

and Fast SCSI. Current SCSI standards include Wide

Ultra 2 SCSI, Ultra 160 SCSI, Ultra 320 SCSI, and Ultra

640 SCSI.

• SCSI-1, SCSI-2, and Fast SCSI use 50-pin connectors.

• Wide SCSIs use 68-pin connectors, while Ultra SCSIs

use 68- or 80-pin connectors.

A SCSI device must match the host adapter based on the

number of pins on the connectors and compatibility stan-

dards between the host adapter and the device.

The host adapter must fit the expansion slot you plan to use.

SCSI host adapters come in either PCI or PCI-Express bus.

For faster data transfer rate, it’s better to use the PCI-Express

bus.

Choose a host adapter that uses bus mastering. Buses that

support bus mastering don’t require a DMA channel for the

SCSI host adapter.

Host adapters are available that allow you use 50-pin and

68-pin connectors along with several standards that allow

you to choose a variety of devices without the need for a

second adapter. Select a host adapter that supports one of

the leading driver standards: Advanced SCSI Programming

Interface (ASPI) or Common Access Method (CAM). Be sure

the host adapter and all device drivers meet the same stan-

dard (Figure 8).

The ASPI or CAM standard also affects the way the host

adapter relates to the OS. Many host adapters provide their

own host adapter drivers to be used by the OS. Manufacturers

of host adapters usually provide the drivers on a CD-ROM.

Select a host adapter that matches the device according to its

electronic signaling method. The cable choices are single-

ended and differential. Don’t mix the two, or you could

damage the devices.

Bus mastering is a feature supported bysome bus architecturesthat enables a controllerconnected to the bus tocommunicate directlywith other devices onthe bus without goingthrough the CPU. Mostmodern bus architec-tures, including PCI,support bus masteringbecause it improvesperformance.


Using USB PortsUsing Universal Serial Bus (USB) ports is less

complicated than using parallel or serial

ports. The OS, together with the USB host

controller, manages the USB port resources.

Like the SCSI bus we just discussed, all

ports and devices on the universal serial

bus use only one IRQ, I/O address, and

DMA channel (Figure 9).

Most system boards have two or more USB

ports. Expansion cards with USB ports are

available for older systems. To install a USB

device you’ll need

• A USB port or expansion card with USB

port and USB firmware

• A USB device driver

Operating System

SCSI Host Adapter

ASPI Standard

ASPI Standard

ASPI StandardASPI Standard ASPI Standard

SCSIDevice Driver 2

SCSIDevice 2

SCSIDevice Driver 3

SCSIDevice 3

SCSIDevice Driver 1

SCSIDevice 1

FIGURE 8—The SCSIdevice driver standardaffects the interaction of the host adapter with thedevice.

One Setof System

ResourcesUsed Here

USB HostController

HandlesMultipleDevices

Operating System(Windows 7)

USB Device Driver

Firmware on SystemBoard Contains theUSB Host Controller

(Bus Master)

USB Firmwareon Device

USB Device FIGURE 9—Only one IRQ, I/O address, and DMAchannel are needed for a USB host controller tomanage multiple devices.


Use the following general steps to install a USB device.

1. Using the Device Manager, verify that the USB host con-

troller driver is installed (Figure 10). If the controller isn’t

installed, install it from the Control Panel by double-

clicking the Devices and Printers icon. If you have

trouble installing the controller, verify that support for

USB is enabled.

2. Plug in the USB device and install its device driver.

For example, if installing a scanner, insert the CD that

came with the scanner in the optical drive and enter

D:\Setup.exe in the Run dialog box. Follow the screen

prompts, if any, to complete installation. Verify that

Windows sees the device in the Device Manager with no

conflicts and without errors.

3. Install the application software to use the device. Conduct

a test operation of the device to confirm that everything

is functioning properly.

FIGURE 10—Using DeviceManager, verify that theUSB host controller isinstalled.


Using FireWire/iLink PortsFireWire/iLink ports are becoming standard on all new sys-

tem boards (Figure 11). There are three types of FireWire/

iLink connectors: a 4-pin connector that doesn’t supply volt-

age to the device, and 6-pin and 9-pin connectors that do

supply voltage.

FireWire/iLink uses isochronous

data transfer, meaning that data is

transferred continuously within

time constraints. This works well

for real-time data like motion cam-

era monitoring. Because data can

be transferred from one device to

another without involving the

CPU, it’s an ideal medium for con-

sumer electronics products like

VCRs, DVDs, TVs, and digital

cameras. A user could record a

home movie with a digital cam-

corder, then download the data

through a digital VCR to a

FireWire/iLink–compliant hard

drive. The PC can later read the

data from the hard drive and use

it as input to video-editing application software. If the digital

camcorder is FireWire/ iLink (IEEE 1394) compliant, it can

download the data directly to the PC.

IEEE 1394.A (the “A” is the revision level) is a FireWire/iLink

standard that supports speeds of 100, 200, or 400 Mbps. It

allows cable lengths up to 4.5 meters (a little more than 14½

feet) and is hot-pluggable. IEEE 1394.B supports speeds

between 800 Mbps and 3.2 Gbps, and cable lengths of up to

100 meters, or more than 300 feet.

To use a FireWire/iLink port, follow these steps:

1. Verify that Windows recognizes that a FireWire/iLink

controller is present on the system board. Using the

Device Manager, look for the FireWire/iLink Bus

Controller listed as an installed device. Click the c

beside the controller in the Device Manager to see the

FIGURE 11—The iLink Port

Hot-pluggable meansyou can plug andunplug a device with-out rebooting or gettingan error message.


specific brand of FireWire/iLink controller the board con-

tains. If the controller isn’t installed or isn’t working,

reinstall the driver. In the Control Panel window, double-

click the Devices and Printers icon. If you have problems

installing the driver, verify that FireWire/iLink support is

enabled.

2. Plug the device into the FireWire/iLink port. Install the

device driver for the device. For example, for a Sony

camcorder, insert the CD that contains the supporting

software into the optical drive and follow the AutoPlay

prompts to install the software. If the disc doesn’t auto-

start, click Start and type <drive>:\Setup.exe in the

Search programs and files field, where <drive> is the

drive letter of your optical drive. When the device is

plugged in and the drivers are installed, you should see

the device listed in the Device Manager under Sound,

Video and Game Controllers. If you don’t see it, turn the

camcorder off and then back on.

3. Install the application software to use the device. Conduct

a test operation of the device to confirm everything is

functioning properly.

For system boards that don’t support FireWire/iLink, you can

install a FireWire/iLink host adapter.


Self-Check 1

At the end of each section of External I/O Devices and Printers, you’ll be asked to pause

and check your understanding of what you’ve just read by completing a “Self-Check”

exercise. Answering these questions will help you review what you’ve studied so far.

Please complete Self-Check 1 now.

1. What are the two types of expansion slots usually found on the system board?

__________________________________________________________

__________________________________________________________

2. Serial and parallel ports were provided on older systems by a(an) _______.

3. True or False? A port designated as COM1 is a parallel port.

4. What type of device connection uses 68-pin and 80-pin connectors?

__________________________________________________________

__________________________________________________________

5. Explain the difference between the SPP and EPP types of parallel ports.

__________________________________________________________

__________________________________________________________

Check your answers with those on page 55.


EXTERNAL I/O DEVICESNow that we’ve covered the various means that the PC pro-

vides to attach devices, let’s look at some of the I/O devices

themselves. Here, we’ll discuss some of the features of I/O

devices and identify the different ways they can attach to the PC.

KeyboardsKeyboards connect to a PC by one of three methods: (1) the

PS/2 (Personal System 2) connector, (2) a USB port, or (3) a

wireless transmitter (Figure 12). Although USB connectors

are hot-pluggable, as a precaution it’s best to consider all

keyboards not hot pluggable. We’ll discuss USB keyboards

later in this section of your study unit.

Pointing DevicesThe most common pointing device is the mouse—more specif-

ically, the wheel mouse or the optical mouse. A wheel mouse

contains a ball, as shown in Figure 13, that moves as it’s

dragged across a surface. Wheels with small holes in them

are turned by the ball’s motion. An optical light sensor looks

6–Pin DIN PS–2Connector Ports(Mini–DINS)

(A) (B)

FIGURE 12—System boards contain ports for the USB or 6-pin PS/2 connector.


through the small holes in the wheels and sends pulses to

the CPU. The X-axis tracks horizontal mouse movement and

the Y-axis tracks vertical mouse movement.

An optical mouse contains a small camera and microchip

(Figure 14). The camera looks through a very small hole at

the work surface up to 1,500 times a second and sends sig-

nals to the CPU via the microchip.

A mouse can have two or three buttons. Software must be

programmed to use these buttons. Nearly all applications use

the left button. Use of the center and right buttons depend

on the operating system and application software. Most mice

also have a scroll wheel between the buttons.

A mouse can be connected to a computer by using

• A dedicated round mouse port directly on the system

board (the mouse is then called a system board mouse or

PS/2 compatible mouse)

• A USB port

Rubber Ball

“Chopper” Wheelfor Y–Axis

“Chopper” Wheelfor X–Axis

X Output

LightDetector

LightDetector

LightSource Light

SourceRoller forX–Axis

Roller forY–Axis

Y Output

FIGURE 13—Inside a Wheel Mouse


• A Y connection with the keyboard so that both the

keyboard and mouse share the same port

• A wireless transmitter

The advantages and disadvantages of each connection type

are based on the resources they require. A system board

mouse is the first choice for most users because the port on

the system board doesn’t take any resources that other devices

might need. If your system board port becomes damaged, you

can switch to a USB port or wireless connection.

To clean a mouse or tracker ball, remove the mouse cover

from the bottom. A few puffs of canned air are normally all

that’s needed. On a mouse that’s especially dirty, use 99%

isopropyl alcohol to clean the wheels and surfaces of the

photo sensors. Warm soapy water is best for cleaning the

ball. Keep alcohol away from the ball because it can dry the

rubber coating.

TinyCameraHole

FIGURE 14—OpticalMouse


MonitorsMonitors are often rated by screen size, resolution, and

refresh rate. Desktop computers typically used cathode ray

tube (CRT) monitors until the early 2000s, when flat-panel

liquid crystal displays (LCDs) began to gain popularity. Note-

book computers use LCDs.

Screen size. Common screen sizes are 15-inch, 17-inch,

19-inch, 21-inch, and 23-inch. When matching a monitor to

a video card, a good rule of thumb is to use a midrange video

card for a mid-sized monitor and a high-end video card for a

large monitor.

Refresh rate. Slow refresh rates make the image appear to

flicker while faster refresh rates make the image appear more

solid and stable.

Resolution. The resolution depends on the video controller

card and software to use the capabilities of the monitor. The

standard resolution for most software is 800 � 600 pixels,

even though monitors are rated on the average of 1024 � 768

pixels. Resolution is set in Windows from the Control Panel

and requires a driver capable of that resolution. High resolu-

tion usually requires more video RAM.

Green monitors. These monitors comply with EPA Energy

Star standards. Requirements for Energy Star certification

vary based on the monitor’s capabilities, but in general, an

Energy Star–certified LCD monitor uses less than 2 watts in

sleep mode and, for most consumer models, less than 100

watts in active mode.

ELF emissions. “ELF” stands for extremely low frequency

(3–30 Hz; 100,000–10,000 km). Most computer monitors

today comply with at the least the minimum industry stan-

dards for ELF emissions.

Flat-panel monitors replaced CRT monitors because they

take up less space, weigh less, use less electricity, and have a

clearer image than CRT monitors (Figure 15). LCD flat-panel

monitors are available in two major types: active matrix and

dual-scan passive matrix. Dual-scan passive matrix is less

expensive and doesn’t have as sharp an image as active

matrix. With dual-scan, two column electrodes are activated


at the same time. In active matrix, an added transistor ampli-

fies the signal at each pixel, enhancing the image.

An LCD panel produces an image using a layered grid of elec-

trodes, a color layer, and a liquid crystal layer. One grid of

electrodes accesses rows while the other accesses columns.

Each intersection of a row and a column electrode form one

pixel on the panel. When electricity is applied to a pixel, it

becomes clear and allows light to pass through, illuminating

(or picking up) color from the color layer.

Flat-panel monitors for desktop PCs are designed to receive

either digital or analog signals from the video card and have

two ports to accommodate either. If the signal is analog, it’s

converted to digital so that the monitor can display it. Video

cards connect digital data from the CPU to analog data. This

data is reconverted back to digital by the monitor. This back-

and-forth conversion decreases image quality. For best

performance, use a digital video card designed for LCDs

when installing an LCD flat-panel monitor.

FIGURE 15—Being much less bulky than the CRT monitor, theflat-panel monitor takes up less space and weighs less as well.


Video CardsVideo cards are known by many names, including

• Graphic adapters

• Video boards

• Graphics cards

• Display cards

The main features to look for in a video card are the bus it

uses and the amount of video RAM it has or can support.

How a Video Card Works

One of the main functions of a video card is to convert digital

signals to analog so a CRT monitor can use them. A RAM

DAC chip on the video card normally does the conversion.

RAM DAC contains three digital-to-analog converters, one for

each of the CRT monitor’s three color guns: red, green, and

blue.

Figure 16 illustrates the four basic functions of a video card:

1. Receiving digital data from the system bus

2. Writing the digital data to video memory

3. Passing the data from video memory to the digital analog

converter (RAM DAC), where it’s converted to analog data

4. Channeling the analog data from RAM DAC to the

monitor

RAM DAC stands for“random access memory digital-to-analog converter.”

RGB VideoPort to Monitor

Video RAM

Video Card

Video Chip Set

PCI Bus Connector

Digital Data

Analog Data

Digital Data

RAM–DAC

FIGURE 16—BasicFunctions of a VideoCard


The Bus Used by the Video Card

The speed and performance of a video card are partially a

function of the bus the card is using. In 1995, video cards

were designed to use the PCI bus. Newer cards use the PCI-

Express bus. Older cards were designed to operate on VESA

local buses (VL-bus), a proprietary local bus, ISA buses, AGP

buses, and EISA buses. Except for PCI and PCI-Express,

these bus types are all obsolete; hardware using the AGP bus

is still available, but has become far less common since PCI-

Express was introduced in 2003.

The fastest bus for video today is PCI-Express. The standard

PCI-Express slot has between 36 and 142 pins, depending on

the number of buses the card has. The chipset, memory, and

RAM DAC on the card determine performance. One method

to improve performance is to allow both the video chipset and

the RAM DAC (input and output) to access video memory at

the same time. This is called dual porting.

The bus external to the video card is the PCI or PCI-Express

bus, but the card itself also has an internal video bus. The

volume of data that can travel on a bus is called bandwidth.

Current video buses use a data path that can be 32 bits, 64

bits, 128 bits, or 256 bits wide. Effective bandwidth of the

card is partially determined by the width of the data path

and the memory on the card.

Graphics Accelerators

A graphics accelerator is a type of video card that has its own

processor. Today’s high demand for fast, high-quality graphics

has made graphics accelerators a necessity.

Processors on graphics accelerator cards are similar to a CPU

but designed to manage video and graphics. Some graphics

accelerator card features include MPEG decoding, 3-D graph-

ics, dual porting, color space conversion, interpolated scaling,

EPA green-PC support, and digital output to LCD monitors.

Graphics accelerator cards speed up the process and reduce

the burden on the system board CPU.


Video Memory

The amount of data received by a video card from the CPU for

each frame (or screen) of data is determined by the screen

resolution (or pixels), number of colors (or color depth meas-

ured in bits), and enhancements to color information called

alpha blending (Table 2). The more data used to create a

single screen, the more memory is needed in the frame buffer

to hold that data. In addition to the frame buffer, the video

card may have other needs for memory, such as for fonts and

custom logos.

Color depth is directly related to the number of bits used to

compose one pixel and can be 4, 8, 16, or 24 bits per pixel.

The larger the number of bits allocated to storing each piece

of data, the greater the number of color shades (color depth)

you have.

ModemsModems are hardware devices that connect computers

together either through phone lines or direct wiring with each

other. When computers are connected together, they form a

Table 2

VIDEO RAM REQUIRED FOR DIFFERENT VIDEO RESOLUTIONS AND COLOR DEPTHS

VideoResolution

4-Bit ColorDepth (16Colors)

8-Bit ColorDepth(256Colors)

16-Bit ColorDepth(65,000Colors)

24-Bit TrueColor (16.7MillionColors)

32-Bit/24-Bit TrueColor with8-Bit AlphaChannel

800 ✕ 600 512 K 512 K 1 MB 2 MB 2 MB

1,024 ✕ 768 1 MB 1 MB 2 MB 4 MB 4 MB

1,152 ✕ 1,024 1 MB 2 MB 2 MB 4 MB 4 MB

1,280 ✕ 1,024 1 MB 2 MB 4 MB 4 MB 6 MB

1,600 ✕ 1,200 2 MB 2 MB 4 MB 6 MB 8 MB


network. There are many different types of modems and net-

works, but most modems today are broadband, meaning

high-speed Internet, as opposed to dial-up modems. Internal

modems are expansion cards typically having two RJ-11

phone line connectors. External modems have their own case

and power supply and usually connect to the computer

through a USB or IEEE 1394 port. External modems also

have RJ-11 phone line connectors to connect with other

modems.

Installing Devices Using Windows 7Now we’re going to cover installation options using Windows 7.

Specifically, we’re going to concentrate on the Device Manager

and Properties screens for new devices. We’ll also focus on the

use of PnP and hot-pluggable devices.

To display the Device Manager screen, select Start, Control

Panel, and System; then click Device Manager (Figure 17).

RJ-11 is an abbrevia-tion for “registered jackfunction 11.” Thisdevice has a two-wiredial tone on a four-pintelephone jack.

FIGURE 17—Opening the Device Manager in Windows 7


You’ll need the administrator level of system security privi-

leges to make any changes using the Device Manager. Make

sure you have this level of clearance from your company’s

system administrator (if it’s a business situation) before you

attempt to access the Device Manager. If you’re a single or

home user, log on using the administrator level of sign-on.

On the Device Manager screen the same options are avail-

able as in other Windows operating systems, but again, in

Windows 7, the options look different. To find the IRQ assign-

ments on your system, select the View pull-down and then

click on Resources by type (Figure 18). Click the arrow next

to Interrupt request. You won’t need to change or even know

these settings, as Windows handles them automatically, but

it can be helpful to know where to find them.

If conflicts are discovered after installing a device, Windows 7

may create a “Conflicting device list.” To get this list and have

the option to correct it, go to Device Manager, right-click on

FIGURE 18—Finding the Resource Assignments Using Windows 7


the device, and select Properties (Figure 19). On the Properties

screen, you’ll see the conflicting device list and a check box

for “Use automatic settings.” Remove the check and select

Change settings. This was common practice in Windows

troubleshooting in versions up to XP, but won’t likely be used

on Vista or Windows 7 machines.

With the preceding differences noted, the Windows 7 Device

Manager is very similar to previous versions of Microsoft

Windows. The screens do look a little different, but the same

options are available to resolve resource allocation conflicts.

Plug-and-Play DevicesPlug-and-play, sometimes abbreviated PnP, is a set of tech-

nologies developed by Microsoft and Intel that allows the

computer system to configure internal expansion cards and

external devices with little or no user intervention. These

FIGURE 19—Resolving Conflicts Using Windows 7


technologies allow you to plug in a card or external device

and use it without setting switches or jumpers. These issues

and all other configuration elements are handled by the sys-

tem. Installation requires the user to have access to a device

driver file and then follow menu-driven commands to install

the device or card. In order for it to work properly, the oper-

ating system, computer BIOS, and device being installed

must all support the PnP specifications, which virtually all

PCs have since the late 1990s.

Most PnP devices are just that—plug them in, Windows con-

figures them, and they’re usable. In some cases, the Install

Hardware Wizard will appear on your screen and ask you

for the device driver for your device. If you require a special

device driver because of applications you’re running, or sys-

tem issues, you may install a new or updated driver for most

devices through the property screen (Figure 20).

FIGURE 20—Device DriverScreen


Hot-Pluggable DevicesSome new products take the PnP idea one step further.

This next step is called hot plugging or hot swapping. Hot-

pluggable/swappable devices were first introduced for use

on notebook PCs that had many external memory devices

installed. The ability to add or remove devices without turning

off the computer has become popular, especially considering

the fact that some PCs take up to three minutes to boot.

Most hot-plugging devices fall into these categories:

• Flash memory cards (a direct transfer from notebooks)

• USB devices (for I/O devices supporting the USB

standard)

• FireWire/iLink (for video devices and cameras)

• Internal PCI/PCI-Express and SCSI devices

USB DevicesIn this section of your study unit we’ll introduce some new

terms associated with USB devices and present an overview

of their uses and limitations. The following is a list of USB

features.

1. There’s no need to open the PC since the devices are

external.

2. I/O devices can be added and removed while the PC is

running (hot pluggable).

Professional Tip

Many new devices support the hot-pluggable specifications, includ-

ing some devices that need to be installed inside the PC. Examples

of these devices are PCI cards and SCSI drives. The advisability of

adding or removing a device from a SCSI bus or the system board

is questionable. In the case of these hot-pluggable devices, you

should turn off your PC and install the device.


3. Device driver selection and configuration is done auto-

matically (PnP).

4. All I/O devices use one socket type.

5. Up to 126 devices are supported per PC.

6. Devices automatically power down when not in use.

7. Most simple devices don’t need their own power source

because the USB cable supplies power.

8. There’s 1.5, 12, and 480 Mbps transfer rates for different

I/O device needs (480 Mbps is supported by USB 2.0).

9. Errors are detected and data integrity is verified.

A typical USB configuration has a single PC with multiple

devices interconnected by USB cables. The data flows in both

directions using these USB cables. Data flowing away from

the PC and toward an external device is considered flowing

downstream. Conversely, the data flowing from the external

device and toward the PC is considered flowing upstream. A

USB hub is installed on the system board or on an expansion

card. This internal hub is called the root hub and typically

contains two or more USB ports. Device configurations of the

external devices range from simple to complex, as shown by

the following terms:

• Hub—A device that contains only additional downstream

ports.

• Simple I/O device—An I/O device with a single upstream

connection that creates or consumes data on behalf of

the PC. An example of a simple I/O device is a USB

keyboard.

• Compound device—A device that includes both an I/O

device and a hub. An example of a compound device is a

monitor that includes a USB port on its base.

• Composite device—A single device that’s able to perform

two or more different functions. An example of a compos-

ite device is a PDA that has a display screen and an

internal wireless modem.

We’ll discuss hubs and I/O devices in a little more detail next.


The Hub

The hub has two major roles in the USB configuration: power

management and signal distribution. An external hub has one

upstream connection and multiple downstream connections

(Figure 21). There’s no limit to the number of downstream

connections, but the most popular hub size has four.

A hub can be self-powered or bus-powered. A self-powered

hub can provide up to 500 mA to each of its ports. The self-

powered hub has an additional power cable attached to it. A

bus-powered hub relies solely on the USB cable for its power

needs.

If the hub is bus-powered, it has a maximum of 500 mA

available. The hub will use 100 mA for itself, and have only

100 mA available for each of the four downstream USB ports.

Although this is enough to enumerate all I/O devices, it’s

typically not enough for most I/O devices to operate. Some

versions of Windows don’t give a visual or audible warning if

a USB device can’t operate because of lack of hub power. In

this case, you could be left wondering why a newly attached

device won’t work.

In the case when the bus-powered hub has more than four

downstream ports, less than 100 mA will be available for

each port. This doesn’t leave enough power to even list an

Downstream Connector Upstream Connector

FIGURE 21—USB CableDownstream andUpstream Connectors


I/O device. When you connect a device to this configuration,

the device actually never installs, which will confuse even an

experienced service technician. This situation could compound

itself if you add a second bus-powered hub onto a port of the

first bus-powered hub. In this case, the second hub uses the

entire 100 mA for itself and again can’t supply enough power

to list additional I/O devices.

Because of the power limitations discussed above, you

shouldn’t use bus-powered hubs except in situations where

there’s a severe limit on external power connections. A fea-

ture of Windows is that the operating system will alert you if

a high-power device is attached to a low-power hub and will

recommend a better system configuration (often using a self-

powered hub).

Another consideration when using a USB hub is that when

an I/O device (which includes a hub) is first attached to a

USB socket, the device always expects 100 mA to be avail-

able. The device uses this power to operate during the listing

stage. The device won’t use more than 100 mA until it’s con-

figured, and if it does, the power for the USB socket will be

disconnected and an error message will be sent to the PC. If

the I/O device requires more than 100 mA for runtime opera-

tion, it can request up to 500 mA from the hub. If the hub

can supply this power, it does so. If the power isn’t available,

the I/O device won’t be configured and an error message is

created. Obviously, if an I/O device requires more than 500

mA for run-time operation, the device must be self-powered.

USB Device Connections

The I/O devices are the items that the PC is most concerned

with. One advantage of USB devices is that you can connect

up to 126 devices to one host. These devices can be con-

nected to the PC using external hubs up to five levels deep

(Figure 22).

One advantage of using USB connections is that all 126

devices use one IRQ, I/O address, and DMA channel. How-

ever, the USB controller requires operating system support to

manage resources, so there’s an impact on system hard-drive

space and RAM.


USB supports three device speeds, low-speed (LS) at 1.5 Mbps

(USB 1.0), full-speed (FS) at 12 Mbps (USB 1.0), and high-

speed at 480 Mbps (USB 2.0); a fourth specification, USB 3.0,

was released in 2008, but hasn’t yet been widely implemented.

USB 3.0 offers data throughput of up to 3.2 Gbps. Low-speed

is used for low-data-rate devices such as mice and keyboards.

The cost of implementing the high-speed data transfer rate is

significantly higher than the low- and full-speed, which is

why you find USB 2.0 supported on more costly devices. The

high-speed data rate is currently used for devices such as

color laser printers, full-color scanners, and CD/DVD drives.

When adding devices to a hub, a high-speed hub is more

complex than a full-speed hub, and it costs more. If you’re

not using USB 2.0 devices, you won’t need a USB 2.0 hub.

The fact that a faster data rate is supported doesn’t mean

that the devices you currently have connected will work

faster. Only devices supporting the USB 2.0 standard can

take advantage of the 480 Mbps rate. A typical system may

have a mixture of USB 2.0 and FS hubs. You can connect a

low-speed device onto a USB 2.0 port, but it would be better

to connect low-speed devices onto an FS or LS port.

Hub

Hub

Hub

Hub

Hub

PowerCord

I/O Device

Host

USB Cablesto More Hubsor I/O Devices

PowerCord

PowerCord

PowerCord

PowerCord

FIGURE 22—I/O DeviceNesting


The maximum cable length between a hub and a device is 5

meters. With five hub levels, any device needs to be located

within a 30-meter radius of your PC. If you require a greater

distance than 30 meters, you’ll need to purchase a repeater.

Repeaters are used to regenerate signals distorted by trans-

mission over distance and can reconstruct a signal to near its

original quality.

Other Add-on DevicesNew devices are frequently created to ease the job of data

entry. Advances in handwriting recognition software, fueled by

personal digital assistants (PDAs), have created devices you

can write on, thus eliminating typing. Voice recognition soft-

ware has also attempted to get rid of typing by having people

talk to their computer; however, this doesn’t work well in

open office situations. Specialized applications like computer-

aided design (CAD) have always supported high-end pointing

devices like digitizing tablets (now supported by USB devices).

The documentation supplied with the device and/or software,

along with the manufacturer’s Web site, supports these items

well. In the following discussion, we’ll cover some conven-

tional and high-usage devices.

USB Keyboards

A USB keyboard looks similar to system board–connected

keyboards. A USB keyboard connects to the USB port in your

computer instead of the older 5-pin Deutsches Insitut für

Normung (DIN) or 6-pin mini-DIN connector. Using the USB

Professional Tip

A USB cable supporting USB 2.0, or even a FS (12 Mbps) data

rate, will transmit data like an antenna. In these cases, cable

shielding is required. Shielding isn’t required for the LS (1.5 Mbps)

rate, so these cables are cheaper. Often there are no visual differ-

ences between shielded and unshielded cables. To prevent the

possibility of using an unshielded cable on a device supporting FS

or USB 2.0, you should only use shielded cables.


connection frees up IRQ 1, but any device other than a key-

board rarely uses this address. The advantage is that the

USB device driver for a keyboard can add features like pro-

grammable extra keys (Internet keys than can store the Web

address of a favorite site) or a flash memory card reader.

Maintenance on these new “smart” keyboards is the same as

for a normal PS/2 style keyboard.

Game Devices

Though the PC joystick was always available as an input

device connected to the sound card’s MIDI port, the new

game devices are almost exclusively USB connected and

programmable. Faster computers with better graphics have

moved video games from the TV onto the PC. To support the

“gamers” out there, the manufacturers of I/O devices have

produced game-oriented, handheld, input devices for PCs

(Figure 23).

The fact that most PC games support the use of a keyboard

has somewhat limited the appeal of these game-specific

devices. Interestingly, more software companies have now

added support for handheld devices connected to PCs. This

has caused an increase in handheld device sales to serious

game players. These devices commonly have device drivers,

and some have optional drivers for specific games. The devices

were designed such that repair isn’t supported by available

FIGURE 23—Game I/O Devices


documentation. A service technician can disassemble one of

these devices and make some base-level repairs (like recon-

necting a cable or replacing a spring). Recommending whether

a handheld device should be repaired or a new device be pur-

chased is a choice that the service technician needs to make

on a device-by-device basis. Maintenance on these devices is

limited to updating device drivers, keeping the device clean,

and keeping it away from heat sources.

Optical Mice

Previous text referred to the two major mouse types (wheel

and optical) and explained the way a wheel mouse works.

Now we’ll go into more depth regarding the workings of an

optical mouse (Figure 14). Optical mice are now much more

commonly used than wheeled mice.

Agilent Technologies first developed the optical mouse in late

1999. As previously mentioned, the optical mouse uses a tiny

camera to take up to 1,500 pictures every second. The mouse

has a small, red light-emitting diode (LED) that bounces light

off a surface onto a complementary metal-oxide semiconductor

(CMOS) sensor. This is the same type of sensor used by digi-

tal cameras. The CMOS sensor sends each image to a digital

signal processor (DSP) for analysis. The DSP, operating at 18

million instructions per second (MIPS), detects patterns of

movement in the images. Based on the change in patterns,

the DSP determines how far the mouse has moved. It then

sends the corresponding change in coordinates to the com-

puter. The computer then moves the cursor on the screen

based on this information. This happens hundreds of times

each second, making the cursor appear to move smoothly.

Optical mice have several benefits over wheeled mice, including

• No moving parts, which means less wear and a lower

chance of failure

• No way for dirt to get inside the mouse and interfere with

the tracking sensors

• Smoother response because of increased tracking resolution

• No requirement for a special surface, such as a mouse pad


The term optical mouse has been used since the inception of

the mouse as a pointing device. The original optical-mouse

technology bounced a focused beam of light off a highly

reflective mouse pad, imprinted with a grid of dark lines,

then into a sensor. Each time the mouse was moved, the grid

interrupted the beam of light and the sensor sent a signal to

the computer. The screen cursor moved a preset amount in

response to the amount and direction of the interruptions.

This kind of optical mouse required the user to orient it at

the correct angle to ensure light beam and sensor alignment.

Scratches and solvents could also damage the mouse pad,

rendering the mouse useless until a replacement pad was

purchased.

Monitors

A compound USB device that’s growing in popularity is the

USB monitor. As stated earlier, a compound device combines

an I/O device with a USB hub. The monitor plugs into a USB

port instead of the standard monitor port on your system or

video board. A nice feature of the USB monitor is that a

powered USB port is included with the monitor (usually at

the base). Having a powered USB port accessible from the

front of your PC is a nice feature, especially for PCs that are

installed into a desk that allows little or no access to the

back of the PC. One disadvantage of USB monitors is that

they don’t always support the same amount of video memory

or some graphics accelerator functions.

Scanners

Technology has advanced to the point that there are full-color

scanners that connect to a PC using a USB cable (Figure 24).

This type of scanner eliminates the need for the device-specific

PCI card and the chance of resource conflicts. Scanners use a

Technology Without an Interesting Name (TWAIN) device driver

and interface. This can cause problems with other TWAIN

installed devices.

The lowered cost of scanners has moved them from business

desktops to home use I/O devices. Scanners using optical

character recognition (OCR) software have eliminated the need


to reenter typed data. This technology enables you to take

printed documents, scan them, convert the raw data to text,

and edit the file with a word processor. Scanners also have

the ability to do a full-color scan of a photograph and store it

in a graphic file for output on a color printer. With advertised

resolutions up to 9,600 � 9,600 and a color depth of 36 bits,

these scanners record information at a higher resolution than

color film, and much higher than most printers can reproduce.

To achieve hardware resolution with a horizontal sampling

rate of 9,600 would require an array of 81,600 sensors. If you

look at the specifications for these scanners, the 9,600 reso-

lutions are listed as a software-enhanced or interpolated

resolution. Interpolation is a process that the scanning soft-

ware uses to create extra pixels in between the ones actually

scanned by the array. These extra pixels are an average of

the adjacent pixels.

Another term used when talking about scanners is color

depth. This refers to the number of colors that the scanner is

capable of reproducing. Each pixel requires 24 bits to create

the standard true color palette of more than 16,000,000

colors (the human eye can perceive only a few million). Almost

all scanners on the market today support this. Many new

scanners offer bit depths of 30 or 36 bits. They still output

only in 24-bit color, but perform internal processing to select

the best possible choice out of the colors available in an

increased palette. It’s questionable whether the human eye

can tell the difference between 24-bit and 36-bit color.

FIGURE 24—Scanner


Desktop Video Cameras

Technology has reduced both the size and the cost of desktop

video cameras, commonly called Web cams (Figure 25). These

small devices have become common I/O devices that are con-

nected to business or home PCs. Connection of these devices

is through a USB cable. Since there’s a severe limit on the

amount of power available through a USB cable, some of these

cameras are self-powered, using batteries and/or plug-in AC

adapters. Check the USB connection of your system for the

power available, before you decide if you need a bus-powered

or a self-powered camera. Many monitors, and most laptop

computers, now include built-in Web cams (Figure 26).

Because of their small size and relatively

low price, these cameras are used for many

business and home applications. Common

uses include video conferencing, digital pho-

tography, and security. In the photographic

and security modes, these cameras use the

TWAIN interface. The software controlling

the camera then converts the files into

Joint Photographic Experts Group (JPEG)

files, which you can store on your com-

puter or share on the Web. Some software

packages can set the camera to take a pic-

ture when movement is detected, or at set

intervals. This makes these inexpensive

devices perfect for home or small-office

security.

FIGURE 25—Desktop Video Cameras or “Web Cams”

Webcam

FIGURE 26—A Web Cam Built into a Monitor


In the video mode, these cameras use many different software-

driven products to create a video. There are many competing

formats for video presented on a PC running Windows (AVI,

Divx, and QuickTime to name a few). There are also software

products created for these Web cams that produce a video

stream that can be broadcast over the Internet. Common

Intermediate Format (CIF) is the video format commonly used

in videoconferencing. It supports a data rate of 30 frames per

second (fps), with 288 lines and 352 pixels per line. When

using a telephone line, another standard format for video-

conferencing, Quarter Common Intermediate Format (QCIF), is

used. This standard transfers one-fourth the amount of data,

or 144 lines and 176 pixels per line.

Professional Tip

Desktop video cameras using a TWAIN interface can cause problems

when installed with a scanner that also uses the TWAIN interface.

Often, even using USB technology, a desktop video camera and a

scanner connected to the same system causes a resource conflict.

If the camera is selected as the enabled TWAIN device, it will turn

on when you try to scan a document. This causes concern when

the scanner doesn’t cycle up, but you notice the camera turn on

and take a picture. Switching the enabled device on the Device

Manager screen or through your application software solves this

problem.


Self-Check 2

1. List three methods that are commonly used to connect a keyboard to the PC.

__________________________________________________________

__________________________________________________________

__________________________________________________________

2. True or False? The best way to clean the ball of a mouse is to use isopropyl alcohol.

3. List three advantages of a flat-panel display over a CRT display.

__________________________________________________________

__________________________________________________________

__________________________________________________________

4. A/an _______ card has its own processor and can produce high-quality graphics quickly.

5. Adding or removing a device from a PC without turning off power is known as _______.



PRINTERSThe printer is the most common and most repairable category

of I/O device. Printers range from simple dot-matrix line

printers to full-color laser printers. In this part of your study

unit, we’ll show you how to support and fix printers as well

as how to connect them into system workgroups. We’ll also

discuss color management, which deals with the problems of

color inconsistency across devices and software. Here you’ll

learn what causes color problems and how color management

tools can help alleviate these problems.

Laser PrintersLaser printers are electro-photographic printers that come in

a wide variety for various uses. Small low-volume personal

printers are usually connected to a single PC, while larger

high-volume printers are often found in networks where they

serve many PCs. Figure 27 shows a laser printer that’s

intended for high-volume use.

FIGURE 27—LaserJet Printer


Laser printers work by placing an electrostatic charge on a

photosensitive drum that changes its electrical conductivity

only in areas where light strikes it. The drum’s surface is

normally insulated from ground, except in areas where light

strikes it, changing electrostatic charges placed on it by the

primary charging roller. The printing principle is based on the

fact that like charges repel, and unlike charges attract.

Figure 28 shows the internal workings of a laser printer.

All major components for most laser printers are self-contained

and user-replaceable. It’s unlikely a computer technician will

be called to address printer problems. However, understand-

ing printer fundamentals can be helpful. The following is a

brief step-by-step overview of the laser-printing process.

Front ofLaser Printer

Erase Lamps

Mirror

Red Filter

PrimaryGrid

Primary Corona Wire

RubberCleaning

Blade

FusingRoller

Cleaner

FusingLamp

SweeperUsed Toner

Paper

LowerFusingRoller

UpperFusingRoller

Feeder BeltStatic

ChargeEliminator

Transfer Corona Wire

Photosensitive DrumRegistration

Rollers

Pick–Up Roller

Cartridge

Developing Magnet

Developing Cylinder

Fresh Toner

Blade

Spinning Scanning Mirror

FIGURE 28—Inside a Laser Printer


Cleaning. The drum is physically wiped clean of any residual

toner with a plastic blade and electrically cleaned of residual

static charges by an eraser lamp.

Conditioning. The drum is conditioned by the primary

charging roller to a uniform static charge. The charge is

usually negative and the same voltage as that of the toner.

Writing. Laser light beams striking the drum cause that

area of the drum’s surface to conduct to ground in propor-

tion to the light’s intensity. This causes those areas on the

drum to become more positive than the negatively charged

toner.

Developing. The negatively charged toner is electrostatically

attracted to the more positive areas of the drum that were

exposed to the laser beam light. The negatively charged toner

is repelled from the negatively charged area of the drum that

wasn’t exposed to the laser light.

Transfer. A positive charge draws the negatively charged

toner off the drum and onto the paper.

Fusing. Heat and pressure bond the microscopic bits of

toner to the fibers of the paper.

Color Laser PrintersOriginally, most laser printers were limited to one color of

toner, but with lower costs and higher demand for color, the

color laser is in many more homes and offices (Figure 29).

Color laser printers work the same way as their monochrome

predecessors, except they go through the printing process

four times. This requires one pass each for cyan, magenta,

yellow, and black. By combining these four basic printing

colors in different proportions, the color laser printer produces

all of the colors of the 24-bit “true color” spectrum supported

by Windows. This makes the printing process about four times

more time-consuming. A printer that prints black copies at a

rate of 20 pages per minute (ppm) may process a color page

at about 5 ppm.

There are three main ways of printing in color, each with its

own advantages. Some models have all four toner and devel-

oper units on a wheel. The printer lays down one color of an


image and then applies this color to the paper. This type of

printer goes through this process for each color. These print-

ers are the slowest but least expensive. Other printers use

the same process to add all four colors to a plate, and then

transfer the complete image to the paper. This process is also

slow but advertises the fact that the color mix is more exact,

making the output more true-to-life. These printers are usu-

ally in the midpriced range and offer more color management

features. The most expensive printers have a laser assembly,

drum head, and toner system for each color. The paper moves

past the different assemblies, collecting all the colors and

fusing the toner to the paper, creating the final product. This

last type has the fastest paper throughput.

Color laser printers are about the same price as high-speed

or high-resolution monochrome laser printers. Support and

maintenance on a color laser printer commonly costs five or

six times more than that of a comparable monochrome

printer. Three colored and one black toner units need to be

purchased to support color printing. The standard price of

the colored toner can be twice that of the black toner, or

more. With more moving parts inside (sometimes four times

FIGURE 29—A Color LaserPrinter


as many), annual maintenance contracts for a color laser

printer are commonly one-half the cost of the printer’s pur-

chase price. This makes the color laser printer, even for most

businesses, a sizable investment.

Color Ink-Jet PrintersColor ink-jet printers are relatively inexpensive and are popu-

lar with home users (Figure 30). An ink-jet printer uses a

print head that moves horizontally across the paper, creating

one line of text with each pass. The paper moves vertically in

synchronization with the print head. The print head puts ink

on the paper using a matrix of very small dots.

Single print-head printers create black by combining the three

generic colors of cyan, magenta, and yellow from the color

ink cartridge. Dual-head printers have a black ink cartridge

that makes a richer black on the paper and is much more

economical.

Two factors that affect the quality of ink-jet printer output

are print-head alignment and paper. Print-head alignment is

important because the black and color inks come from differ-

ent cartridges. The cartridges must therefore be aligned to

make the proper color blends. The holes that dispense the

ink can be in different places on every installed cartridge.

Even if only one cartridge is being installed, alignment of the

print heads is required. The printer control panel using the

FIGURE 30—A ColorInk-Jet Printer


alignment option handles the alignment of the print heads.

On many ink-jet printers, this control panel is automatically

activated at the administrator’s PC when an ink cartridge is

installed. Follow the instructions on the screen for proper

alignment of the print heads.

The second factor that impacts good color reproduction is the

quality of the paper. The paper should be listed for use in an

ink-jet printer. Many copier papers do support printing on an

ink-jet, but not all. The second thing to look for is the bright-

ness of the paper. The closer the brightness number is to 100,

the closer the paper is to white. Papers labeled as “photo”

paper for ink-jets often have a brightness of 95 or higher and

a glossy surface. Be aware that after printing, the ink on

glossy papers will smear until it dries. Some software applica-

tions take into consideration the brightness of the paper, but

most don’t. If your application allows you to change color

values depending on paper brightness, make sure you set

this value with every change of paper type.

Color Management With advances in technology, every media has moved from

black-and-white to color. The youth of this country have

never seen black-and-white TV shows or magazines. In 1981,

when IBM came out with the PC, the only color on a screen

was CRT green or amber. One of the first major upgrades on

the PC’s list of options was a color screen supporting four

colors. Over the decades, color has become standard on PCs,

with the current standard being the 24-bit true color specifi-

cation. A majority of PCs and their connected displays now

support 24-bit color resolution, or the even higher 32-bit

specification. Almost all Web sites present their materials in

full color.

Having everything in color has become commonplace in the

world of computers, but there’s one problem. The problem is

the challenge of finding a way to get consistent colors from

page to screen to printer. Consistent color across your dis-

play and printer is important to the quality of the documents

you’re creating. Page designers, as well as more casual users,

want to have the images they’ve created look consistent when


displayed on the monitor, printed, or even posted on the

Internet. Everyone wants a true what-you-see-is-what-you-

get (WYSIWIG, pronounced “wizzy-wig”) image across their

whole computer system. The problem with this is that the

color needs to stay visually consistent between the scanner,

monitor, application software, and final printer output. This

has been very difficult to achieve because of two major road-

blocks: different color systems and different gamuts.

Different Color Systems

White light contains three components of color: red, green,

and blue (RGB). Human eyes perceive color based on how

much of each color reaches them. Monitors and scanners are

based on the additive color system using RGB. Starting at

black, they add red, green, and blue until the desired color is

achieved. The highest levels of all three colors make a color

that’s perceived as white. All images on a monitor, or copied

using a scanner, radiate varying amounts of RGB.

Printers are based on the subtractive color system, usually

using the colors cyan, magenta, yellow, and black (CMYK).

Printed material creates images by reflecting light off of sub-

stances such as ink, dye, wax, and toner. Printers begin with

white (the presence of white light) and subtract RGB to achieve

colors and black. Cyan, for instance, subtracts red and allows

the reflection of green and blue.

Different Gamuts

Each device has a particular range of colors that it’s able to

produce; this is known as the device gamut. The gamut of a

device is determined by the color properties of the device, as

well as the lighting of the room where the device is. A color

monitor can normally reproduce nearly twice as many colors

as a printing press. Knowing this underlines the problem with

color. The picture seen on the monitor can be reproduced on

the Web with good results. Sometimes it even looks good on

the ink-jet or laser output that was coordinated with the

monitor. The problem arises when you send the data file to

the print shop for mass production and the colors change.


Another even more bothersome problem can crop up when

the gamut of the same type of device varies. The color man-

agement setup on the application software being used may

need multiple color configurations for different equipment in

the office. For instance, the gamuts of scanners depend on

the process (flatbed, drum, or sheet feed) the scanner uses,

the resolution and color depth supported, and the media

scanned (matte, reflective, or transparent).

If you have a computer I/O device capable of capturing,

displaying, or printing color pages, you’re likely to have expe-

rienced some of the problems in dealing with color on a PC.

Using the color management tools on a particular device

won’t solve all of your problems, but it will allow you to have

more control over the final product.

The use of a color management system (CMS) is recommended

for commercial users of color. A color management system

compensates for the ways different devices handle the same

colors by using profiles to translate color information. With

this technology, colors appear consistent on any device and

application used in the document’s process. This is a com-

plex problem with many differing solutions.

Color Management on Laser and Ink-Jet Printers

Color management on a color laser printer is controlled by

software included with the device driver. The cost of color

printing using a laser printer is high enough to make setting

up the color output well worth the time. You should use a

standard color management tool that can be set to the same

parameters as your application software. The generic Cyan/

Magenta/Yellow/Black Key (CMYK) standard is a good place

to start. Some color laser printers have their own color man-

agement profile. This profile can be installed into most color

graphics programs. Remember, to check the colors that have

been adjusted, a copy must be printed. By carefully tracking

the variables being changed, the cost of this project can be

controlled.

Color management on color ink-jet printers is similar to that

of laser printers. The color reproduction is controlled using

the Color Management tab on the Printer Properties screen.

Adjustments can be made to change the different color bands


and image quality. The look of these color management panels

is brand specific. Check the documentation that accompanied

your printer for the use of color management features.

Sharing PrintersPrinters can be shared over a network using one of three

methods:

• A printer can be attached to a PC using the PC’s parallel

port. The PC can then share the printer with the network.

• A network printer with embedded logic to manage net-

work communication can be connected directly to a

network.

• A computer dedicated as a print server can control sev-

eral printers connected to a network.

Network print services allow a computer to share a printer

connected to it, and to use printers that are connected to

other computers on the network. In Windows you can share a

printer as easily as sharing a file.

Use the following steps to share a printer using Windows 7:

1. Be sure that file and printer sharing is installed. Click

Start, click Control Panel and then click the Network

and Sharing Center icon. Click Change adapter settings,

right-click the Local Area Connection icon, and click

Properties.

2. If File and Printer Sharing for Microsoft Networks isn’t

listed, click Install to install the feature.

3. Select Service and click Add from the list of network

services, then select File and Printer Sharing for

Microsoft Networks and click OK. You may be asked to

insert the Windows DVD and to reboot.

4. Share the printer by clicking Start and clicking Devices

and Printers. The Devices and Printers window will open.

5. Right-click the printer you want to share. From the

shortcut menu select Printer Properties. Click the

Sharing tab, and click the Share this printer check box.


6. In the Share name field, give the printer a share name.

Click OK.

7. The printer should now be listed in the Network

Neighborhood group of other computers on the network.

Products for Network PrintersJetDirect is an installed hardware option with a supported

software component. The JetDirect product is often used in

midsized workgroups that have a number of HP or HP-

compatible printers on their network. The combination of

hardware and software allows your HP printer to become a

print server on your network. When the software is used, it

will find all compatible printers on the network for you. At

this point, an individual with administrator level of security

can configure all of the compatible printers on the network.

JetDirect is designed for use on any supported HP printer with

an EIO slot. JetDirect software supports the connections made

through the JetDirect card’s USB, serial and/or LocalTalk

ports, in addition to the HP printer’s existing parallel port.

You can connect a supported printer to a network that

includes a Windows PC, iMac, Power Mac G3/G4, or UNIX

workstation that uses a serial printer connection.

Practical ExerciseIn this Practical Exercise, you’ll find the color management

scheme used on your monitor and modify some of the

variables. Check your results on page 55.

1. Go to the Color Management screen. You can find this by

clicking on Start, clicking Control Panel, and then click-

ing Display. Next, click Adjust resolution in the left

pane, click on Advanced Settings, then select the Color

Management tab.

2. Click Color Management; this screen will either list the

monitor and profile being used, or show the Color

Management screen for your monitor (Figure 31).


3. If the Color Management tab displays the current

monitor type and default profile, this is the end of this

exercise.

4. If the screen displays adjustable variables, then make

note of all beginning settings. Modify the settings one at

a time to see the differences.

5. Reset the variables to their original settings.

FIGURE 31—Preset Monitor Profile


Self-Check 3

1. What are the six steps of laser printing?

__________________________________________________________

__________________________________________________________

2. True or False? Paper quality has little effect on color printing.

3. What term is used to describe the ability to see on the monitor what the final output will look like?

__________________________________________________________

__________________________________________________________

4. Photo paper for ink-jet printing will normally have a brightness factor of _______ or higher.

5. True or False? Good print quality on an ink-jet printer depends on proper head alignment.



NOTES

Self-Check 1

1. PCI (Peripheral Component Interconnect) and PCI-Express

2. I/O controller card

3. False

4. SCSI

5. The SPP allows data flow in only one direction while EPP

is bidirectional.

Self-Check 2

1. PS/2 connector; wireless connector; USB port

2. False

3. Flat-panel monitors take up less space, are lighter, use

less electricity, and have a sharper image.

4. graphics accelerator

5. hot-plugging or hot-swapping

Self-Check 3

1. Cleaning, conditioning, writing, developing, transferring,

and fusing

2. False

3. WYSIWIG (what-you-see-is-what-you-get)

4. 95

5. True

Practical Exercise

Your results will depend on which variable was changed.

Most changes make obvious differences. For example,

changing the green channel will change the amount of

green illumination added to the screen image without

affecting the red or blue channels.

55

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Study Unit - External I-O Devices and Printers

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