PC Maintenance: Preparing for A+ Certification

PC Maintenance: PC Maintenance: Preparing for A+ Preparing for A+

CertificationCertificationChapter 24: ModemsChapter 24: Modems

Chapter 24 ObjectivesChapter 24 Objectives

Understand and change modem Understand and change modem communication settingscommunication settings

Explain modem standardsExplain modem standards Differentiate between types of modemsDifferentiate between types of modems Set up DUN connectionsSet up DUN connections Test and troubleshoot modemsTest and troubleshoot modems Use a terminal applicationUse a terminal application Use AT commandsUse AT commands

Baud Rate and BPSBaud Rate and BPS

Baud rate: number of cycles per secondBaud rate: number of cycles per second Bits per second (bps) is a multiple of baud Bits per second (bps) is a multiple of baud

raterate

UARTsUARTs

Universal Asynchronous Universal Asynchronous Receiver/TransmitterReceiver/Transmitter

Converts between serial and parallel dataConverts between serial and parallel data External modem does not need an UART External modem does not need an UART

chip because it uses the one in the port to chip because it uses the one in the port to which it is attachedwhich it is attached

Modem Communication SettingsModem Communication Settings

Data bitsData bits Start bitsStart bits Stop bitsStop bits Parity bitsParity bits Flow controlFlow control Error detection and compressionError detection and compression

Data Bits, Start Bits, Stop BitsData Bits, Start Bits, Stop Bits

Each packet contains either 7 or 8 data Each packet contains either 7 or 8 data bitsbits

Leading bit is start bit, always 0Leading bit is start bit, always 0 Ending bit is stop bit, always 0, optionalEnding bit is stop bit, always 0, optional

Parity BitsParity Bits

Can be even parity or odd parityCan be even parity or odd parity Count the number of 1s in the dataCount the number of 1s in the data With even parity:With even parity:

If the number is already even, parity bit is set If the number is already even, parity bit is set to 0to 0

If odd, parity bit is set to 1, making the total bit If odd, parity bit is set to 1, making the total bit count evencount even

With odd parity, the oppositeWith odd parity, the opposite With no parity, not done at allWith no parity, not done at all

Parity BitsParity Bits

Example of even parity:Example of even parity:

Flow ControlFlow Control

Flow between the modem and the COM Flow between the modem and the COM portport

Mostly an issue with external modemsMostly an issue with external modems Hardware type: Ready to Send (RTS) Hardware type: Ready to Send (RTS)

Clear to Send (CTS)Clear to Send (CTS) Software-type: XON/XOFFSoftware-type: XON/XOFF

Changing Communications Changing Communications Settings in Windows 9xSettings in Windows 9x

From Modems in Control Panel, view From Modems in Control Panel, view modem’s Propertiesmodem’s Properties

Changing Communications Changing Communications Settings in Windows 9xSettings in Windows 9x

To set flow control, click Advanced button To set flow control, click Advanced button to see Advanced Connection Settingsto see Advanced Connection Settings

Changing Communications Changing Communications Settings in Windows 2000/XPSettings in Windows 2000/XP

From Phone and Modem Options in Control Panel, From Phone and Modem Options in Control Panel, view modem’s Propertiesview modem’s Properties

Modem StandardsModem Standards

V.34: An early modem standardV.34: An early modem standard 28.8Kbps28.8Kbps Eventually upped to 33.6KbpsEventually upped to 33.6Kbps

56KFlex and X256KFlex and X2 Two competing standards for 56KbpsTwo competing standards for 56Kbps Eventually merged into the V.90 standardEventually merged into the V.90 standard


V.92V.92 Current standard for 56Kbps modemsCurrent standard for 56Kbps modems Like V.90 but with improvementsLike V.90 but with improvements

QuickConnectQuickConnect PCM UpstreamPCM Upstream Modem-on-HoldModem-on-Hold


V.42bis and V.44V.42bis and V.44 Standards for compressing dataStandards for compressing data They work alongside V.90 or V.92They work alongside V.90 or V.92 V.44 is the newer standard, with higher V.44 is the newer standard, with higher

compression ratios (20 to 60% higher than compression ratios (20 to 60% higher than V.42bis)V.42bis)

Hardware vs. Software Hardware vs. Software Controlled ModemsControlled Modems

Hardware modemsHardware modems Have their own controller and BIOS chipHave their own controller and BIOS chip Do not require a specific OSDo not require a specific OS Can be internal or externalCan be internal or external Superior performanceSuperior performance More expensiveMore expensive Not very common anymore (unfortunately)Not very common anymore (unfortunately)

Hardware vs. Software Hardware vs. Software Controlled ModemsControlled Modems

Software modemsSoftware modems Require Windows-based controller softwareRequire Windows-based controller software Work only with WindowsWork only with Windows Are always internalAre always internal Are less expensiveAre less expensive Might not work with some applications that Might not work with some applications that

expect a hardware modemexpect a hardware modem

Internal vs. External ModemsInternal vs. External Modems

InternalInternal PCI, ISA, PC CardPCI, ISA, PC Card Less expensiveLess expensive Require resources directly (IRQ, etc.)Require resources directly (IRQ, etc.)

ExternalExternal Legacy COM or USBLegacy COM or USB More expensiveMore expensive Require power connection Require power connection Do not require resources directly (IRQ, etc.)Do not require resources directly (IRQ, etc.)

Fax and Voice ModemsFax and Voice Modems

Nearly all modems are fax-capableNearly all modems are fax-capable Group 1 and Group 2Group 1 and Group 2: 300 bps, now obsolete: 300 bps, now obsolete Group 3Group 3 : Several standards : Several standards

ITU V.27 (4,800 bps)ITU V.27 (4,800 bps) ITU V.29 (9,600 bps)ITU V.29 (9,600 bps) ITU V.17 (14,400 bps, current standard)ITU V.17 (14,400 bps, current standard)

Voice capability (“voice modem”)Voice capability (“voice modem”) Works with answering machine softwareWorks with answering machine software

Installing an Internal ModemInstalling an Internal Modem

Set jumpers on modem to define IRQ Set jumpers on modem to define IRQ (needed only on very old equipment)(needed only on very old equipment)

Installing an Internal ModemInstalling an Internal Modem

Insert into any Insert into any free slot of the free slot of the appropriate appropriate typetype

Connect phone Connect phone line and, line and, optionally, optionally, telephonetelephone

Installing an External ModemInstalling an External Modem

Connect to COM or USB portConnect to COM or USB port Connect to AC powerConnect to AC power Attach phone line and, optionally, Attach phone line and, optionally,

telephonetelephone

Troubleshooting Modem Troubleshooting Modem ProblemsProblems

Check physical connectivityCheck physical connectivity Use Device Manager to check for problemsUse Device Manager to check for problems Check resource allocationsCheck resource allocations Make sure usable driver is installedMake sure usable driver is installed Test with Windows testing utilityTest with Windows testing utility

Testing a Modem in Windows 9xTesting a Modem in Windows 9x

1.1. Open Open ModemsModems from Control Panelfrom Control Panel

2.2. Click Click DiagnosticsDiagnostics tabtab

3.3. Select the modemSelect the modem

4.4. Click Click More InfoMore Info

Testing a Modem in Windows Testing a Modem in Windows 2000/XP2000/XP

1.1. Open Open Phone and Phone and Modem OptionsModem Options from from Control PanelControl Panel

2.2. Click the modemClick the modem

3.3. Click Click PropertiesProperties

4.4. Select Select DiagnosticsDiagnostics tabtab

5.5. Click Click Query ModemQuery Modem

TAPI PropertiesTAPI Properties

Telephony Application Programmers Telephony Application Programmers Interface (TAPI)Interface (TAPI) Set of codes that allow programmers to use Set of codes that allow programmers to use

the modem and phone in applicationsthe modem and phone in applications Standard set of TAPI properties in WindowsStandard set of TAPI properties in Windows User-configurableUser-configurable Multiple dialing locations possibleMultiple dialing locations possible


Windows 9x: Windows 9x: Telephony icon Telephony icon in Control Panelin Control Panel

Click New to Click New to create a new create a new dialing locationdialing location


Windows 2000/XP: Windows 2000/XP: Phone and Modem Phone and Modem Options in Control Options in Control PanelPanel

Dialing Rules tabDialing Rules tab

Double-click a Double-click a location to edit its location to edit its propertiesproperties

Dial-Up NetworkingDial-Up Networking

Direct connection from one computer to Direct connection from one computer to another, such as PC to ISPanother, such as PC to ISP

Requires a modemRequires a modem Point to Point Protocol (PPP) most Point to Point Protocol (PPP) most

commoncommon Serial Line Internet Protocol (SLIP) less Serial Line Internet Protocol (SLIP) less

common, used for some UNIX serverscommon, used for some UNIX servers

Creating a DUN Connection in Creating a DUN Connection in Windows 9x/MeWindows 9x/Me

1.1. Install Dial-Up Networking if needed Install Dial-Up Networking if needed (Windows component)(Windows component)

2.2. Open Dial-Up Networking folder:Open Dial-Up Networking folder: Windows 95/98:Windows 95/98: choose Dial-Up Networking choose Dial-Up Networking

from My Computer windowfrom My Computer window Windows Me:Windows Me: Start > Settings > Dial-Up Start > Settings > Dial-Up

NetworkingNetworking

Creating a DUN Connection in Creating a DUN Connection in Windows 9x/MeWindows 9x/Me

3.3. Double-click Make New ConnectionDouble-click Make New Connection

4.4. Follow the promptsFollow the prompts

Internet Connection WizardInternet Connection Wizard

Another way of creating a DUN connection in Another way of creating a DUN connection in Windows 98/MeWindows 98/Me

Specifically for an ISP connectionSpecifically for an ISP connection Start the Wizard:Start the Wizard:

Windows 98:Windows 98: Start > Programs > Accessories > Start > Programs > Accessories > Internet Tools > Internet Connection WizardInternet Tools > Internet Connection Wizard

Windows Me:Windows Me: Start > Programs > Accessories > Start > Programs > Accessories > Communications > Internet Connection WizardCommunications > Internet Connection Wizard

Work through the promptsWork through the prompts

Creating a DUN Connection in Creating a DUN Connection in Windows 2000Windows 2000

Two choices of wizards:Two choices of wizards: Network Connection WizardNetwork Connection Wizard

Can be used either for private DUN or for InternetCan be used either for private DUN or for Internet If you choose Internet, it closes itself and opens If you choose Internet, it closes itself and opens

Internet Connection Wizard.Internet Connection Wizard. Internet Connection WizardInternet Connection Wizard

Creating a DUN Connection in Creating a DUN Connection in Windows XPWindows XP

Internet Internet Connection Connection Wizard Wizard integrated into integrated into the the New New Connection Connection WizardWizard

Start new Start new Connection Connection Wizard and Wizard and follow the follow the promptsprompts

Using a Terminal ProgramUsing a Terminal Program

Direct text-Direct text-based based connection connection between two between two PCsPCs

Hyperterminal Hyperterminal comes with comes with WindowsWindows

Half-Duplex and Full-DuplexHalf-Duplex and Full-Duplex

Duplex: ability to send and receive on the Duplex: ability to send and receive on the same wiresame wire Half-duplex: Send and receive, but not Half-duplex: Send and receive, but not

simultaneouslysimultaneously Full-duplex: Send and receive simultaneouslyFull-duplex: Send and receive simultaneously

Set Up Duplex in HyperterminalSet Up Duplex in Hyperterminal

Choose File > PropertiesChoose File > Properties On the Settings tab, click ASCII SetupOn the Settings tab, click ASCII Setup

Binary File Transfer in a Terminal Binary File Transfer in a Terminal ProgramProgram

Uses a different protocol from regular Uses a different protocol from regular ASCII textASCII text

Common protocols includeCommon protocols include ZMODEM (best choice)ZMODEM (best choice) YMODEMYMODEM XMODEMXMODEM KERMITKERMIT

Using AT CommandsUsing AT Commands

AT command set originally developed by AT command set originally developed by Hayes, a modem manufacturerHayes, a modem manufacturer

Each command line begins with AT for Each command line begins with AT for “attention”“attention”

Requires terminal program to be in Requires terminal program to be in command mode before issuingcommand mode before issuing

Entering AT Commands in Entering AT Commands in HyperterminalHyperterminal

At Connection Description box, click At Connection Description box, click CancelCancel

Type ATE1 and press Enter. (You will not Type ATE1 and press Enter. (You will not see what you typed.)see what you typed.) E1 is the command to switch to full duplex E1 is the command to switch to full duplex

modemode

Now type whatever AT commands are Now type whatever AT commands are neededneeded

Example AT CommandsExample AT Commands

ATDT5552311ATDT5552311 AT: AttentionAT: Attention DT: Dial the following number using Tone DT: Dial the following number using Tone

dialingdialing 5552311: Number to dial5552311: Number to dial

ATZATZ AT: AttentionAT: Attention Z: ResetZ: Reset

Other Uses for AT CommandsOther Uses for AT Commands

Enter commands Enter commands in modem’s in modem’s Properties boxProperties box

Other Uses for AT CommandsOther Uses for AT Commands

Configure modem settings in AOLConfigure modem settings in AOL

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