pc maintenance: preparing for a+ certification chapter 24: modems
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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
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
Modem StandardsModem Standards
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
Modem StandardsModem Standards
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
TAPI PropertiesTAPI Properties
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
TAPI PropertiesTAPI Properties
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
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