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 (V.FC&V.FASTmodemregister'dumps')...   	 X      ThesearetheprofilesthatworkbestonCALLINGmodemsw/RTS/CTScable:MicrocomDeskPortES28.8unit(port@57400ifatrue16650AFNisactive);ACTIVEPROFILE:B1E1L3M3N1Q0TV1W2X4Y0&C1&D2&G0&J0&K3&Q5&R1&S0&T4&X0&Y0S00:000S01:000S02:043S03:013S04:010S05:008S06:002S07:050S08:002S09:006S10:090S11:050S12:050S18:000S25:005S26:001S36:007S37:000S38:020S44:020S46:138S48:007S95:040STOREDPROFILE0:B1E1L3M1N1Q0TV1W2X4Y0&C1&D2&G0&J0&K3&Q5&R1&S0&T4&X0S00:000S02:043S06:002S07:050S08:002S09:006S10:090S11:050S12:050S18:000S36:007S37:000S40:105S41:134S46:138S95:040STOREDPROFILE1:B1E1L3M1N1Q0TV1W2X4Y0&C1&D2&G0&J0&K3&Q5&R1&S0&T4&X0S00:000S02:043S06:002S07:050S08:002S09:006S10:090S11:050S12:050S18:000S36:007S37:000S40:105S41:134S46:138S95:040HayesOptima288V.FCunit(port@57400ifatrue16650AFNisactive):ACTIVEPROFILE:B1B16B76E1L1M3N1Q0TV1W2X4Y0&A0&C1&D0&G0&K3&Q9&R0&S0&T4&U0&X0&Y0S00:000S02:043S03:013S04:010S05:008S06:002S07:050S08:002S09:006S10:014S11:050S12:050S25:005S26:001S36:007S37:015S38:020S46:010S48:007S49:064S50:192S108:001S109:4094S110:002STOREDPROFILE0:B1B16B76E1L1M1N1PQ0V1W2X4Y0&A0&C1&D0&G0&K3&Q9&R0&S0&T4&U0&X0S00:000S02:043S06:002S07:050S08:002S09:006S10:014S11:050S12:050S25:005S26:001S36:007S37:015S38:020S46:010S48:007S49:064S50:192S108:001S109:4094S110:002STOREDPROFILE1:B1B16B76E1L1M1N1PQ0V1W0X4Y0&A0&C1&D2&G0&K3&Q5&R0&S0&T4&U0&X0S00:000S02:043S06:002S07:050S08:002S09:006S10:014S11:095S12:050S25:005S26:001S36:007S37:000S38:020S46:002S48:007S49:064S50:192S108:001S109:4094S110:002USRV.FASTbetaunit(port@57400ifatrue16650AFNisactive);USRoboticsCourier28800HSTDualStandardSettings...̀B2C1E1F1M1Q0V1X7̀BAUD=57600PARITY=NWORDLEN=8̀DIAL=HUNTONHOOKTIMER̀&A3&B1&C1&D0&G0&H1&I0&K3&L0̀&M4&N0&P0&R2&S0&T5&X0&Y1%R0̀S00=000S01=000S02=043S03=013S04=010S05=008̀S06=002S07=060S08=002S09=006S10=007S11=040̀S12=050S13=000S14=000S15=000S16=000S17=000̀S18=000S19=000S20=000S21=010S22=017S23=019̀S24=150S25=005S26=001S27=000S28=008S29=020̀S30=000S31=000S32=001S33=000S34=000S35=000̀S36=000S37=000S38=000S39=000S40=000S41=000̀S42=000S43=000S44=015S45=000	   	 .+8   Todisablecall-waitingonoutgoingcalls-InMTEZ(Press<Atl>Dthen'O'fortheoptionsscreen).InLOCALprefixesput*70,andinLongDistanceput*70,1(doNOTleaveouttheCOMMA).Youcannotdisablecall-waitingonincomingcalls.YoumustusethesameformatforALLphonebookentries(includinglocalcalls)xxx-xxx-xxxx	   	 `		   BASICATCOMMANDS(defaultvaluesarehighlighted)   	 X      CommandDescriptionATAttentioncharactersATAAnswercommandATA/Re-ExecutelastcommandTransmitCarrierSignalATC0Transmitcarriersignaloff.(default)ATC1Transmitcarriersignalon.DialModifiersDialOptionsDescriptionATDnoneDial.(ATDfollowedbyphonenumber)ATDLnoneRe-dial.ATDPnonePulse(rotary)dial.10pulsesper̀second.ATDTnoneTouchtonedial(DTMF).ATDW1-255secWaitfordial-tone.Defaultis50̀seconds.ATD,0-255secPause.Defaultis2seconds.ATD@noneWaitforquietanswer.ATD!noneInitiatehookflash.ATD;noneReturntocommandstateafterdialing.ATD^noneDisablecallingtone.ATDS=0-3noneDialstorednumber.CommandDescriptionATE0Disablesechoingofthecommandstothescreen.ATE1Enablesechoingofthecommandstothescreen.̀(default)ATH0Instructsmodemtogoon-hook.ATH1Instructsmodemtogooff-hook.ATI0Displaystheproductidentificationcode.ATI1Displaysthechecksum.ATI2DisplaysROMchecksumasOKorERROR.ATI3Displaysthefirmwarerevisionlevel.SpeakervolumeATL0Offorlowvolume.ATL1Lowvolume.(default)ATL2Mediumvolume.ATL3Highvolume.SpeakercontrolATM0Disablesthemodemspeaker.ATM1Turnsspeakeronuntilcarrierhasbeendetected.̀(default)ATM2Instructsthemodemspeakertostayonallofthètime.ATM3Enablesspeakerafterdialinguntilconnectionis̀established.AutomodeenableATN0Requiresspeedoftheconnectionbethatspecified   	 p0.;   ЀbythevalueofS37.ATN1Permitshandshakingatanyspeedsupportedbỳbothmodems.(default)ReturntoonlinestatemodeATO0Switchesthemodemfromcommandmodetoon-̀linemodewithoutdialing.ATO1Switchesfromcommandmodetoon-linemodeaǹinitiatesanequalizerretrainsequenceduring2400̀baudbpsoperation.ModeresponsesATQ0Enablesresultcodestobeissuedtothescreen.̀(default)ATQ1Disablesresultcodestobeissuedtothescreen.ResultcodeformatATV0Numericformat.ATV1Verbalformat.(default)ErrorcorrectionmessagecontrolATW0Errorcorrectioncallprogressnotreported.̀(default)ATW1Callprogressreported.ATW2Callprogressnotreported.ConnectxxxxmessagèreportsDCEspeed.ExtendedresultcodesATX0Disablesmonitoringofbusytonesunlessforced̀otherwisebycountryrequirements;sendsonlyOK,̀CONNECT,RING,NOCARRIER,ERRORandNÒANSWERresultcodes.ATX1Disablesmonitoringofbusytonesunlessforced̀otherwisebycountryrequirements;sendsonlyOK,̀CONNECT,RING,NOCARRIER,ERROR,NÒANSWERandCONNECTXXXXresultcodes.ATX2Disablesmonitoringofbusytonesunlessforced̀otherwisebycountryrequirements;sendsonlyOK,̀CONNECT,RING,NOCARRIER,ERROR,DIALTONE,NOANSWER̀andCONNECTXXXXresultcodes.ATX3Enablesmonitoringofbusytones;sendsonlyOK,̀CONNECT,RING,NOCARRIER,ERROR,NÒDIALTONE,NOANSWERandCONNECTXXXX.ATX4Enablesmonitoringofbusytonesandsendsall̀messages.(default)ControllongspacedisconnectATY0Disableslongspacedisconnect.(default)ATY1Enableslongspaceconnect.SoftresetandrestoreprofileATZ0Restoresstoredprofile0.(default)ATZ1Restoresstoredprofile1.+++Escapecharacters.Theescapecharactersarèknownas+++.Theywillswitchfromon-linemodetòcommandmodewhilepreservingtheconnectionwiththeoǹlinemodem.   	 p0.;   ExtendedATCommandsCommandDescriptionDatacarrierdetect(DCD)signalAT&C0ForcesDCDsignaltobeonatalltimes.(default)AT&C1DCDonindicatespresenceofdatacarrier.Dataterminalready(DTR)signal.InterpretstheONtoOFFtransitionoftheDTRsignalfromtheDTEaccordingtothe&Qsettings.AT&D0&Q0,5,6.DTRignored.̀&Q1,4.Modemhangsup;autoanswernotaffected.̀&Q2,3.Modemhangsup;autoanswerinhibited.̀(default)AT&D1&Q0,1,4-6.Asynchronousescapesequence.̀&Q2,3.Modemhangsup;autoanswerinhibited.AT&D2&Q0-6.Modemhangsup;autoanswerinhibited.AT&D3&Q0,1,4-6.ModemdoesasoftresetasiftheATZcommand̀werereceived;̀&Q2,3.Modemhangsup;autoanswerinhibited.AT&FRecallsfactorydefaults.Instructsthemodemtousèthefactorysetparameters.DTE/ModemflowcontrolAT&K0Disableflowcontrol.AT&K3EnableRTS/CTS(defaultfordatamodem)AT&K4EnableXON/XOFF.AT&K5EnabletransportXON/XOFF.AT&K6EnablebothRTS/CTSandXON/XOFF(defaultforFAXmodem)NoteonFlowControl.XON/XOFFisasoftware-basedflowcontrolmethod,usingstandardASCIIcontrolcharacterstopauseorresumedatatransmission.RTS/CTSpacing,ahardware-basedmethod,usesanelectricalsignal.Signalsareexchangedasfollows:RECEIVERTRANSMITTERCTSON------------>STARTSENDINGCTSON<-----------RTSON(readytosend)CTSOFF------------>RTSOFF(stopsending)CommandDescriptionSelectpulsedialmake/breakratioAT&P0Selectsamake/breakratioof39/61at10pps.̀USandCanada.(default)AT&P1Selectsamake/breakratioof33/67at10pps.̀UKandHongKong.AT&P2Sameas0exceptat20pps.AT&P3Sameas1exceptat20pps.AsynchronousmodeAT&Q0DirectAsynchronousmode.AT&Q5Modemnegotiatesanerror-correctedlink.̀(default)AT&Q6Selectsasynchronousoperationinnormalmodè(i.e.speedbuffering).   	 p0.;   DataSetReady(DSR)signalAT&S0CausesDSRsignaltobeactiveatalltimes.̀(default)AT&S1CausesDSRsignaltobeactiveaccordingtothèCCITTspecification.TestanddiagnosticsAT&T0Terminatesanytestinprogress.AT&T1Executesthelocalanalogloopbacktest.AT&T3Executesthelocaldigitalloopbacktest.AT&T4Enablesthemodemtoacceptarequestfromàremotemodeforadigitalloopbacktest.(default)AT&T5Instructsthemodemtodenyarequestfromàremotemodemforadigitalloopbacktest.AT&T6Executestheremotedigitalloopbacktest.AT&T7Executestheremotedigitalloopbacktestwithàselftest.AT&T8Executestheremoteanalogloopbacktestwithàselftest.AT&VViewcurrentconfigurationanduserprofile.Storeuserprofile.Savesthecurrentconfigurationintonon-volatileRAMasoneoftwouserprofiles.AT&W0Savesasuserprofile0.AT&W1Savesasuserprofile1.DesignatedefaultuserprofileAT&Y0Selectsuserprofile0.AT&Y1Selectsuserprofile1.StoredphonenumberAT&Z=0Storesa36digitdialstring.AT&Z=1Storesa36digitdialstring.AT&Z=2Storesa36digitdialstring.AT&Z=3Storesa36digitdialstring.MNPOperationTheV.FASTClassModemsupportsalloftheprecedingclasses.ThefollowingATCommandsapplytotheMNPprotocol.Defaultvaluesarehighlighted.MaximumMNPBlockSize.Usethiscommandtotransmitsmallerblocksofdatainareliabledatalinkconnection.AT\A0setmaximumblocksizeto64characters.AT\A1setmaximumblocksizeto128characters.̀(DEFAULT)AT\A2setmaximumblocksizeto192characters.AT\A3setmaximumblocksizeto256characters.TransmitBreak.Whenthiscommandisenteredduringanon-MNPconnection,abreaksignalissenttotheremotemodem.Thelengthofthebreakis100timesthenparameter(1-9)inmilliseconds.Thedefaultis3.AT\B3(DEFAULT)   	 p0.;   ModemtoModemFlowControl.Enablesordisablesmodemtomodemflowcontrolduringanormalmodeconnection.Thiscommandisignoredwhenerrorcorrectionisselected.AT\G0Disablesflowcontrol(XON/XOFF)(DEFAULT)AT\G1Enablesflowcontrol(XON/XOFF)BreakControl.DeterminesthemodemresponsewhenaBREAKisreceivedfromtheDTEortheremotemodem.Thevaluesoftheparametersvarybasedonthethreefollowingconditions:(1)WhenabreakisreceivedfromtheDTEduringNORMALorMNPmode:AT\K0,2,4modementerscommandmodewithoutsendingabreaktòtheremotemodem.AT\K1modemclearstheterminalandmodembuffersand̀sendsabreaktotheremotemodem.AT\K3modemdoesnotclearthebuffers,butsendsabreak̀totheremotemodem.AT\K5modemsendsabreaktotheremotemodeminsequencèwithanytransmitteddata.(DEFAULT)(2)WhenabreakisreceivedfromtheremotemodemduringNORMALmode:AT\K0,1modemclearstheterminalandmodembuffersand̀sendsabreaktothelocalDTE.AT\K2,3modemdoesnotclearthebuffersbutsendsabreak̀tothelocalDTE.AT\K4,5modemsendsabreakinsequencewithanydatàbeingbuffered.(DEFAULT)(3)WhenabreakisreceivedfromtheDTEduringDIRECTMODEmode:AT\K0,1,3modemsendsabreaktotheremotemodemandenters̀commandmode.AT\K2,4,5modemsendsabreaktotheremotemodem.(DEFAULT)MNPBlockTransferControl.DetermineswhetherornotthemodemwilluseblockorstreammodeforMNPlink.AT\L0usesstreammodeforMNPlinkconnections(DEFAULT)AT\L1usesblockmodeforMNPconnectionsErrorCorrectionOperatingMode.Selectstheoperatingmodethemodemuseswhileconnected.AT\N0NORMAL(speedbuffering)mode.AT\N1DIRECT(pass-through)mode.AT\N2RELIABLELINKmode.Specifieserrorcorrectionfor̀themodem-to-modemconnectionAT\N3AUTO-RELIABLELINKmode.Attemptserror-correctioǹconnectionbutwillfallbacktonormalmodeif̀unabletoestablishanMNPlink.AT\N4LAPMerrorcorrectionmode.AT\N5MNPerrorcorrectionmode   	 p0.;   SplitSpeedOperation.Supportsasplit-speedDCE/DTEinterfaceforapplicationswhichrequireatransmitspeedof75bpsandreceivespeedof1200bpsattheDTEinterface.AT\W0disables(DEFAULT)AT\W1enablesMNPLinkNegotiationSpeed.Controlstheconnectionspeedforlinknegotiations.AT*H0linknegotiationoccursatthehighestsupported̀speed.(DEFAULT)AT*H1linknegotiationoccursat1200bps.S-RegistersThissectiondefinesthepurposeofthemodemregisters,andsequentiallyliststheregistersanddescribestheirfunctions.Theseregistersaffectvariousoperatingcharacteristicsandallowyoutoobtaininformationaboutthemodem,aswellastestthemodem.Eachregisterhasafactory-setvalue,whichyoucanreadorchangetofityourneeds.ReadingaRegisterValueToreadthecurrentvalueofaregister,type:ATSn?[ENTER],wherenisaregisternumber.ATSn?Sn?[ENTER]fromthecommandmode.ToreadtheregistervaluesofS0andS1,typeATS0?S1?[ENTER].Themodemwilldisplaythefirstregistervalue,acarriagereturn,thenextregistervalue,acarriagereturn,andOKor0.ChangingaRegisterValueTochangearegistervalue,usetheSncommand(ATSn=v),wherenisaregisternumberandvisthenewvalueyouwanttoassigntotheregister.Type:ATS0=3[ENTER]tohavethemodemautomaticallyansweronthethirdring.Thefollowingtableliststhemodem'sregistersandtheirfunctions.Reg.RangeUnitsDefaultDefinitionS00-255rings2Auto-answerS10-255rings0CountincomingringsS20-255rings43Escapecharactervalue.S30-127ASCII13Carriagereturncharacter.S40-127ASCII10Linefeedcharacter.S50-32ASCII8Backspacecharacter.S62-255seconds2WaittimeforBlindDialing.   	 p0.;   S71-255seconds50Waitforcarrierafterdial.S80-255seconds2Pausetimefordialdelay.S91-255seconds6/10Carrierdetect.S101-255seconds14(1.4)LostCarriertoHangUpDelay.S11Reserved.S120-255seconds50(1)Escapecodeguardtime*.(*inone-fiftiethsecondincrements)S13Reserved.S14BitMappedAA,hexBitmappedregisters.S15ReservedS16BitMapped80,hexModemtestoptions.S17Reserved.S180-255seconds0Testtimer.S19Reserved.S20Reserved.S21BitMapped00,hexBitmappedregisters.S22BitMapped75,hexBitmappedregisters.S23BitMapped07,hexBitmappedregisters.S240-255seconds0SleepInactivityTimer.S250-255seconds5AsynchronousDTRDelay.S260-255seconds1DelayInterval.S27BitMapped9,hexBitmappedregisters.S28BitMappedBitmappedregistersS29Reserved.S300-255seconds0InactivityTimer.S31BitMappedOptions.S320-255ASCII17XONCharacter.S330-255ASCII19XOFFCharacter.S34-35Reserved.S36BitMappedOptions.S370-120TelephoneLineSpeedNOTE:ThisisinterlinkedwiththeATFncommand.Ifaninvalidnumberisentered,thenumberisacceptedintotheregister,butS37willreactasthoughthedefaultvaluehasbeenentered.Bits0-30=Attemptautomodeconnection(ATF0)(DEFAULT)̀1-3=Attempttoconnectat300bps̀4=Reserved̀5=Attempttoconnectat1200bps(ATF1)̀6=Attempttoconnectat2400bps(ATF4)̀7=AttempttoconnectatV.23(ATF3)̀8=Attempttoconnectat4800bps(ATF6)̀9=Attempttoconnectat9600bps(ATF8)̀10=Attempttoconnectat12Kbps(ATF9)̀11=Attempttoconnectat14.4Kbps(ATF10)̀12=Attempttoconnectat7200bps(ATF7)Bits4-7ReservedS380-255seconds20DelayBeforeForcedHangup.S39BitMappedBitMappedRegisters.S40BitMappedBitMappedRegisters.S41BitMappedBitMappedRegisters.S42-45Reserved.S46136or138138DataCompressionControl.NOTE:136enableserrorcorrectionwithnocompression;138enableserrorcorrectionWITHcompression.   	 p0.;   S480,7,1287V.42Negotiation.NOTE:0disablesnegotiationandproceedswithLAPM;7enablesnegotiation;and128disablesnegotiationandproceedswithfallbackactionspecifiedinS36.ThedefaultforS36istoattemptanMNPconnection.S49-81Reserved.S823,7,128128BreakHandlingOption.S86N/AConnectionFailureCauseCode.S910to-15dBm10PSTNTransmitLevel.S920to-15dBm10FaxTransmitLevel.S95Bit-MappedNAExtendedResultsCodes.NOTE:BitvaluesaredefinedasfollowsforS95:0=CONNECTCODEindicatesDCEspeedinsteadofDTEspeed.1=AppendARQ(automaticrepeatrequest)toverboseCONNECTXXXX̀resultcodeifprotocolisotherthannone.2=EnableCARRIERXXXXresultcode.3=EnablePROTOCOLXXXXresultcode.5=EnableCOMPRESSIONresultcode.Bits4,6,and7arereserved.ResultCodesResultNumericCodeValueDescriptionOK0Modemsuccessfullyexecutedacommandline.̀CONNECT1Connectionmadeat300bps.̀RING2Modemdetectedanincomingcall.̀NOCARRIER3Modemlostorcouldnotdetectaremotecarrier̀signalwithintheRegisterS7time.̀ERROR4Modemfoundanerrorinthecommandline.̀CONNECT5Modemestablishedaconnection1200at1200̀1200bps.NO6Modemdidnotdetectadialtonewithin5DIALTONEsecondsaftergoingoff-hook.BUSY7Modemdetectedabusysignal.NOANSWER8Fivesecondsofsilencewasnotdetectedwheǹusingthe@commandinthedialcommandline.CONNECT06009Modemestablishedaconnectionat600bps.CONNECT240010Modemestablishedaconnectionat2400bps.CONNECT480011Modemestablishedaconnectionat4800bps.CONNECT960012Connectionmadeat9600bps.   	 p0.;   Ї+FCERROR+F4Faxcarriererror.CONNECT720013Connectedasdatamodemduringan7200answer.̀CONNECT1200014Connectionmadeat12000bps.CONNECT1440015Connectionmadeat14400bps.CONNECT1920016Connectionmadeat19200bps.CONNECT3840017Connectionmadeat38400bps.CONNECT5760018Connectionmadeat57600bps.CONNECT22Modemreturnsthisresultcodewhenupon75TX/1200RXestablishingaV.23originateconnectioǹwhenthemodemhasbeeninstructedtòreporttheDTEspeedtotheDTEupoǹconnecting.CONNECT23Modemreturnsthisresultcodewhenupon1200RX/75RXestablishingaV.23answerconnectioǹwhenthemodemhasbeeninstructedtòreporttheDTEspeedtotheDTEupoǹconnecting.CARRIER30040Carrierrateof300bps.CARRIER44V.23backwardchannelhasbeendetected.1200/75̀CARRIER45V.23forwardchannelhasbeendetected75/1200CARRIER120046Carrierrateof1200bps.CARRIER240047Carrierrateof2400bps.CARRIER480048Carrierrateof4800bps.CARRIER720049Carrierrateof7200bps.CARRIER960050Carrierrateof9600bps.CARRIER1200051Carrierrateof12000bps.CARRIER1440052Carrierrateof14400bps.COMPRESSION:66ThemodemhasconnectedinMNPclass5CLASS5andCOMPRESSIONmessagereportinghasbeeǹenabled.COMPRESSION67ThemodemhasconnectedinV.42bisandV.42bisCOMPRESSIONmessagereportinghasbeenenabled.COMPRESSION:69ThemodemhasconnectedwithoutdataNONEcompressionandCOMPRESSIONmessagereporting̀hasbeenenabled.PROTOCOL:76Modemhasconnectedwithoutanyformoferror   	 p0.;   NONE*correction.PROTOCOL:77ModemhasconnectedintheV.42LAPMmodeLAPM*LAPMmodeoferrorcorrection.PROTOCOL:80ModemhasconnectedintheMNPmodeoferrorALT*correction.PROTOCOL:81ModemhasconnectedintheMNP10modeALT*CELLULAR*PROTOCOLmessagereportinghasbeenenabled.	   	 `	   ЀWhatYouNeedToKnowAboutModems---------------------------------------------------------------------------DistributionNotice:Thisdocumentmaybedistributedbyelectronicbulletinboardsandcommercialon-lineservices.Thisdocumentmaynotbeeditedorchangedinanywayforredistribution.ThisarticleisPartOneofathree-partreportentitled"TheJoyofTelecomputing."AsaplainASCIIfile,itcannotcontainanyoftheillustrationsandgraphicelementsprovidedintheprintedversion.Forfurtherinformationabout"TheJoyofTelecomputing,"seeAppendixC.Thisarticleshouldbeusefultoanyoneinterestedinhigh-speedmodems(or2400bpsmodemswithMNP-5orV.42bis).Mostmodemsmentionedinthisarticleareexternalunits.Thesemodemscanbeusedonanymicrocomputersystem,beitaPC,aMacintoshoranAmiga.Althoughonlycertaincommunicationprogramsareusedasexamples,thediscussionsaboutsettingupsoftwareapplytopackagesnotcoveredherein.Itisassumedthatthereaderknowsthebasicsaboutgoingonline.Forexample,wewouldnotdiscusshowtoconnectanexternalmodemtoyourcomputer,norwouldweexplainwhat8-N-1means.ThisfileisintheIBMASCIIformat.Eachlineendswithalinefeedandacarriagereturn.IfyouuseaMacintosh,openthefilewithatexteditorandgetridofthelinefeeds.(IrecommendMcSink,asharewaretexteditorwidelyavailable.JustlaunchMcSinkandopenthefile,thenchoosetheConvertmenuandselectStripLinefeeds.)Toprintthisdocument,usea10-pitch(12charactersperinch)mono-spacedfontsuchasCourier.Everyefforthasbeenmadetosupplycompleteandaccurateinformation.However,informationcontainedhereinissubjecttochangewithoutnoticeandshouldnotbeconstruedasacommitmentbytheauthorwhoassumesnoresponsibilitiesforanyerrorsthatmayappear.Trademarks:Theauthorhasattemptedthroughoutthisdocumenttodistinguishproprietarytrademarksfromdiscriptivetermsbyfollowingthecapitalizationstyleusedbythemanufacturer.-----------------------------------------------------------------------------CONTENTSIntroductionModulationProtocols̀2400bpsmodems̀High-speedmodems̀V.32̀V.32bis̀U.S.RoboticsHST̀TelebitPEP̀HayesExpress96̀CompuComCSP̀ThingstocomèV.fast̀ISDNErrorControlProtocols̀V.42andMNP-4̀V.42&MNP-4canprovideerror-freeconnections̀V.42andMNP-4canimprovethroughput̀AreMNP4/V.42useful?   	 p0.;   DataCompressionProtocols̀MNP-5&V.42bis̀AreMNP-5&V.42bisuseful?̀CompressionbySoftwarevs.MNP-5/V.42bis̀LocalFlowControlandDataBuffering̀Macintoshandhigh-speedmodems̀PCandUARTProfilesofHigh-speedmodems̀ATI9600etc/èCompuComSpeedModemChamp/Star/Storm̀Hayesmodems̀ImageCommunications:Twincom96/42̀Intel9600EX&14.4EX̀PracticalperipheralsPM9600SA&PM9600̀Prometheusmodems̀Telebitmodems̀U.S.Roboticsmodems̀ZoomV.32TurboModems̀ThingstocomeBuyingaHigh-speedModem̀ShouldyoupaytheextraforaV.32bismodem?̀Shouldyoubuyamodemwithaproprietarymodulationprotocol?̀Shouldyoubuya2400bpsmodemwithV.42bis?̀BewareoftheadsSettingUpSoftwaretoWorkwithHigh-speedModems̀TheProperSoftwareSetup̀DoesYourSoftwareInitializetheModemProperly?̀DoesYourSoftwareConfigureItselftoMatchtheModemSettings?̀WhyYouMayNeedtoChangetheInitializationString̀EditingtheInitializationString̀MatchSoftwareSettingsTotheModemSettingsConfiguringPopularCommunicationsSoftwaretoWorkwithHigh-speedModems̀Procomm2.0̀Telix̀Qmodem̀HyperAccess5̀CrosstalkforWindows̀MicroPhoneII(forMacintosh)̀ZTerm(forMacintosh)OtherSettingsforYourCommunicationsSoftwarèTelephoneNumber̀DialString:ATDT̀8-N-1or7-E-1(databits-parity-stopbits)̀Halfvs.FullDuplex:LocalEchòTerminalEmulatioǹCommPort̀FileTransferProtocols̀ASCIÌXmodem̀Xmodem-1K̀Ymodem̀Ymodem-g̀Zmodem̀Kermit̀Sealink̀Whichfiletransferprotocolshouldyouuse?AppendixA:ResourcesAppendixB:HowtoreachtheauthorAppendixC:About"TheJoyofTelecomputing"   	 p0.;   IntroductionBuyingandusingamodemusedtoberelativelyeasy.Notsolongago,almostallmodemsare1200or2400bpsunitsandtheyareallcompatiblewiththeHayesSmartmodems(althoughsomearemoreHayes-compatiblethanothers).Howtimehaschanged.Today,modemsnotonlyrunfaster,theyarealsoloadedwithfeatureslikeerrorcontrolanddatacompression.Suddenly,youareconfrontedWithallthebuzzwords:V.32,V.32bis,V.42,V.42bis,MNP-5,LAP-M,etc.thatdotheymean?Andwhatdotheymeantoyou?Tomakethemostofahigh-speedmodem,youneedtounderstandthreedifferentkindsofprotocolsandtherelationshipsamongthem.Theyarethemodulationprotocols,errorcontrolprotocolsanddatacompressionprotocols.ModulationProtocolsModemstandsforMOdulator/DEModulator.Amodemconvertsdigitalsignalsgeneratedbythecomputerintoanalogsignalswhichcanbetransmittedoveratelephonelineandtransformsincominganalogsignalsintotheirdigitalequivalents.Thespecifictechniquesusedtoencodethedigitalbitsintoanalogsignalsarecalledmodulationprotocols.Thevariousmodulationprotocolsdefinetheexactmethodsofencodingandthedatatransferspeed.Infact,youcannothaveamodemwithoutmodulationprotocols.Amodemtypicallysupportsmorethanonemodulationprotocols.Therawspeed(thespeedwithoutdatacompression)ofamodemisdeterminedbythemodulationprotocols.High-speedmodemsaremodemsthatfeaturemodulationprotocolsat9600bpsorhigher.A2400bpsmodemwithdatacompressionthatcantheoreticallyyielda9600bpsthroughputisnotahigh-speedmodem."CCITT"isaFrenchacronymfortheInternationalTelegraphandTelephoneConsultativeCommittee.CCITT,aUnitedNationsagency,isaninternationaltelecommunicationsstandardscommitteethatmakesrecommendationsonabroadrangeofsubjectsconcerningdatacommunications.2400bpsModemsA2400bpsHayes-compatiblemodemtypicallysupportsthefollowingmodulationprotocols:̀Bell103(300bpsU.S.Standard)̀Bell212A(1200bpsU.S.Standard)̀CCITTV.22(1200bpsstandardusedoutsidetheU.S.)̀CCITTV.22bis(2400bpsInternationalStandard)̀Some2400bpsmodemsalsosupportthefollowingprotocols:̀CCITTV.21(300bpsstandardusedoutsidetheU.S.)̀CCITTV.23(1200/75and75/1200bps,usedinEurope)Inthepast,most2400bpsmodemsdonotsupportanyerrorcorrectionordatacompressionprotocols.Recently,however,manymodemmanufacturershaveintroduced2400bpsmodemswithextrafeatureslikedata   	 p0.;   compression,errorcorrectionandfaxcapability.̀High-speedModemsTherearetwostandardmodulationprotocolsforhigh-speedmodems:V.32andV.32bis.BotharestandardsestablishedbytheCCITT.̀V.32Thisisthestandardfor9600(and4800)bpsmodems.CCITTV.32isadoptedbytheCCITTin1984.Butthemarkethasnottakenoffuntilrecently.V.32modemsusedtocostmorethanmodemsusingproprietarymodulationprotocols(HayesintroducedtheSmartmodem9600,aV.32modem,in1988witha$1999pricetag).Butitisnolongertrue.Atpresent,streetpricesformostV.32modemarebelow$500.EverymodemmanufacturerismakingV.32modemsnow.Packet-switchingnetworkslikeSprintnet(Telenet)andCompuServearealsostartingtosupportV.32modems.Companiesthatmakemodemswithproprietarymodulationprotocolsaremakingmodemswith"dualstandard."U.S.Robotics,Telebit,HayesandCompuComallhavemodemsthatsupportV.32andtheirownproprietaryprotocols.̀V.32bisV.32bis,establishedinearly1991,istheCCITTstandardfor14400bpsmodems.AV.32bismodemalsocanfallbackto12000,9600,7200and4800bps.V.32bisisdownwardlycompatiblewithV.32.Unlike2400bpsmodemswhereasinglemodulationprotocol(V.22bis)issupportedbyallmodemmakers,thereareseveralproprietarymodulationprotocolsusedbymodemsfromdifferentmanufacturers.U.S.RoboticsHST(HighSpeedTechnology)UntiltherecentsurgeofV.32modems,theU.S.RoboticsHSTwasthedefactostandardinthePC-basedBBScommunity.U.S.RoboticsintroducedtheCourierHSTmodemin1986andpioneeredthemarketforhigh-speedmodemsintheIBMPCenvironment.TheimmensepopularityoftheHSTmodemswaspartlyduetothegenerousdiscountprogramU.S.RoboticsofferedtotheBBSSysops(SYStemOPerators).ManymodemmanufacturershaveimplementedsimilarSysopdiscountprograms,butmostBBSsysopsremainloyaltotheU.S.Roboticsmodems.TheoriginalCourierHSTmodemranat9600bps.U.S.RoboticslaterimprovedthespeedoftheCourierHSTto14400bps.AlthoughU.S.RoboticsremainscommittedtotheHSTmodems,therearenowthreedifferenthigh-speedCouriermodemsavailable:theCourierHST(whichonlysupportstheHSTprotocol),theCourierV.32bis(whichonlysupportsV.32bis)andtheCourierHSTDualStandard(whichsupportsboththeHSTandtheV.32bisprotocols).TelebitPEP(PacketizedEnsembleProtocol)TelebitintroducedtheTrailBlazerin1985thatemployedaproprietarymodulationprotocolcalledPEP.WhiletheCourierHSTispopularamongBBS,TelebitmodemsdominatetheUNIXUUCPandUsenetcommunities.(Usenet,UUCPandtheInternetarediscussedinPartIIof"TheJoyofTelecomputing").TheTrailBlazerPlusowesitssuccesspartlytoitsbuilt-insupportfor   	 p0.;   theUUCPg-protocol,thusallowingefficientandflawlessUUCPsession.PEPalsoperformswellevenwithnoisytelephonelines.Theactualthroughputisaround14400bps.TheTrailBlazerPlushasaninstalledbaseofmorethan120,000units.Telebitalsointroducedacheaper(andslower)PEPmodem,theT1000,in988.̀HayesExpress96Hayesenteredthehigh-speedmodemarenain1987withtheintroductionoftheV-seriesSmartmodem9600.ThemodemusedaproprietarymodulationprotocolcalledExpress96(alsoknownasHayes"PingPong"protocol).TheV-seriesmodemshavenotbeenassuccessfulastheU.S.RoboticsortheTelebitmodems.̀CompuComCSP(CompuComSpeedProtocol)WhileeverymodemmanufacturerisjumpingontheV.32bandwagon,CompuCombuckedthetrendandcameoutwiththeSpeedModemChampinearly1991.It'sa9600bpsmodemwithaproprietarymodulationprotocolcalledCSP.TheSpeedModemChamphasonestrongsellingpoint.ItistheonlymodemwithaproprietaryprotocolthatcostslessthanagenericV.32modem.TheinternalSpeedModemChampispricedat$169.Anexternalversionisavailablefor$199.HundredsofPC-basedbulletinboardsystemshaveinstalledtheSpeedModemChamp.TheChampalsoworksasaHayes-compatible2400bpsmodemwithMNP2-4errorcontrolandMNP-5datacompression.Twomodemscanestablishaconnectiononlywhentheyshareacommonmodulationprotocol.Toconnectathighspeed,twomodemshavetosupportthesamehigh-speedmodulationprotocol.Therefore,amodemwithaproprietarymodulationprotocolcanonlyestablishahigh-speedconnectionwithanothermodemfromthesamemanufacturer.AU.S.RoboticsHSTmodemcanonlyestablishahigh-speedconnection(at9600or14400bps)withanotherHSToranUSRDualStandardmodem.ACourierHSTmodemcannotestablishahigh-speedconnectionwithaCourierV.32bismodem.Theycanonlyconnectat2400bps.(Allhigh-speedmodemsinthemarketsupporttheCCITTV.22bismodulationprotocol).Ontheotherhand,twoV.32modemscantalktoeachotherat9600bps.Theydonothavetobefromthesamemanufacturer.TwoV.32bismodemscantalktoeachotherat14400bps.AV.32modemcantalktoaV.32bismodemat9600bps.ThingstocomeV.fastCCITTisworkingonanewmodemstandard,dubbedV.fast.Ifallgoeswell,thenextmodemstandardcanmaterializebefore1993.AV.fastmodemisexpectedtoreacharawspeedof19,200-24,000bpsoverstandarddial-uptelephonelines.ISDNInacoupleofyearswemaynotneedmodemsatall.IntegratedServicesDigitalNetwork(ISDN)hasbeencomingforyears.WhenwillISDNreallybecomeavailablefortherestofus?Itdependsonyourlocaltelephonecompany.Itisestimatedthatbytheendof1994abouthalfthetelephoneconnectionsintheU.S.willhasaccesstoit.WithISDN,youwon'tneedamodemsincenomodulationordemodulationwillbenecessary.You   	 p0.;   willneedanISDNadapterinstead.AnISDNlinecarriesthreedigitalchannels:two"B"channelsthatcarryvariouskindsofdataat64,000bpsanda"D"channelat16,000bpsthatcancarrycontrolsignalsorserveasathirddatachannel.AsingleISDNchannelcantransferuncompresseddatabidirectionallyat64,000bps.Combinethatwithadatacompressionschemeandyouwillbeabletotransferdataathundredsofkilobitspersecond.Eventually,ISDNwillprovidewidelyavailable,low-costdigitalcommunicationsforvoiceanddatacommunication.UntilISDNisfirmlyinplace,high-speedmodemswillbewithusforawhile.ErrorControl(Error-Correcting,ErrorCorrection)ProtocolsBesideshigh-speedmodulationprotocols,allcurrentmodelsofhigh-speedmodemsalsosupporterrorcontrolanddatacompressionprotocols.V.42andMNP-4Therearetwostandardsforerrorcontrolprotocols:MNP4andV.42.TheMicrocomNetworkingProtocol,MNP,isdevelopedbyMicrocom.MNP2to4areerrorcorrectionprotocols.MNP-5isadatacompressionprotocol.V.42isestablishedbyCCITT.V.42actuallyincorporatestwoerrorcontrolschemes.V.42usesLAP-M(LinkAccessProcedureforModems)astheprimaryschemeandincludesMNP-4asthealternatescheme.Therefore,aV.42modemwillbeabletoestablishanerror-controlledconnectionwithamodemthatonlysupportsMNP4.Amodemthatusesaproprietarymodulationprotocolmayalsouseanon-standarderrorcontrolprotocol.Forexample,HayesV-seriesSmartmodem9600supportsanerrorcontrolprotocolcalledLAP-B.CompuCom'sSpeedModemChampalsousesanon-standarderrorcontrolprotocol.̀V.42&MNP-4canprovideerror-freeconnectionsModemswithouterrorcontrolprotocols,suchasmost2400bpsHayes-compatiblemodems,cannotprovideerror-freedatacommunications.Thenoiseandotherphonelineanomaliesarebeyondthecapabilitiesofanystandardmodemtodelivererror-freedata.V.42(andMNP2-4)copeswiththephonelineimpairmentsbyfilteringoutthelinenoiseandautomaticallyretransmittingcorrupteddata.IfyouhaveusedastandardHayes-compatiblemodem,youprobablynoticesomegarbledcharacters(like"@8d_\nw`[ce")showuponyourscreenfromtimetotime.Whentwomodemsestablishanerror-controlledconnection,theyaresaidtohaveareliablelinkandarecapableoffilteringoutthosegarbledcharacterscausedbythelinenoise.Noticethatthelinenoiseisstillthere,itjustdoesnotshowuponyourscreenorthescreenontheremotesystem.ThefilteringprocessusedbyV.42(andMNP2-4)issimilartotheerrorcorrectionschemeusedbyfiletransferprotocols(suchasXmodem).Thetwomodemsuseasophisticatedalgorithmtomakesurethatthedatareceivedmatchwiththedatasent.Ifthereisadiscrepancy,thedataisresent.   	 p0.;   ЇWhatisthedifferencebetweenerrorcontrolprotocols(suchasV.42)andfiletransferprotocols(suchasXmodem)?Foronething,filetransferprotocolsprovideerrordetectionandcorrectiononlyduringfiletransfers.Filetransferprotocolsdonotprovideanyerrorcontrolwhenyouarereadinge-mailmessagesorchattingwithotherpeopleonline.Inotherwords,anerrorcontrolprotocolis"on"allthetimeduringyouronlinesessionandfiletransferprotocolsare"on"onlysomeofthetimes,namelywhenyouaresendingorreceivingfiles.Eventhoughanerrorcontrolprotocolis"on"allthetime,westillneedfiletransferprotocolswhentwomodemsestablishareliablelink.Amodemworkswithbitstreams,timingandtones.Itdoesnotunderstandwhatafileis.Whenyoudownloadoruploadafile,yourcommunicationssoftwareneedstotakecareofthedetailsrelatedtothefile:thefilename,filesize,etc.Thisishandledbythefiletransferprotocolwhichdoesmorethanerror-checking.Somefiletransferprotocols,mostnotablyYmodem-gandImodem,aredevelopedtohandlefiletransferwithoutperforminganyerror-checking.TheideaofusingaprotocollikeYmodem-gistoeliminatetheredundancythusimprovethetransferspeed.Ymodem-gandImodemshouldonlybeusedwithmodemsthatprovidebuilt-inerrorcontrolprotocols.Thesefiletransferprotocolsdonotprovideanyerror-detectionorrecoverycapability.Ifaproblemoccursduringthefiletransfer,thetransfersessionwillbeaborted.ProtocolslikeYmodem-gorImodemdependonthemodemstoprovideassurancefortheintegrityofdatabeingtransferred.However,youshouldknowthatareliablelinkbetweentwomodemsdoesnotprovideabsoluteguaranteeforthedataintegrityduringfiletransfer.Whenyoucallaremotecomputer,therearereallythreelinksinvolvedintheprocess.Besidesthelinkbetweenthetwomodems,therearestillonelinkbetweenyourcomputerandyourmodemandanotherlinkbetweentheremotemodemandtheremotecomputer.WhentwomodemsmakeareliableconnectionusingV.42orMNP4,onlythedataintegritybetweenthetwomodemsisensured.Itisstillpossibleforerrorstooccurateitherendbetweentheserialportandthemodem(inthecable)orinthecomputeritself.(Fortunately,sucherrorsarerare.)Forextraprotection,youmaystillwanttouseafiletransferprotocol-suchasZmodem-whichalsoperformserrorcheckingevenifyouhaveareliablelinkwiththeremotesystem.ThereisacommonmisconceptionthatYmodem-gismuchfasterthanotherfiletransferprotocols.AlthoughYmodem-gissignificantlyfasterthanYmodem,itofferslittleoverZmodem.Zmodemhasproventobeextremelyefficient.(Seebenchmarkbelow)̀FilenameYmodemYmodem-gZmodem̀-------------------------------------------------------̀the-wave.txt1527cps3261cps3296cps̀dayrpt.arc76110421025̀dayrpt.wks124423142337̀sunset.arc745987965̀sunset.pic129725942588̀text109k.arc81410891064̀text109k.txt135128122885   	 p0.;   ЇNote:TheseventestfilesusedthroughoutthisarticleareavailableontheHayesBBS(800-874-2937).ItisanexcellentsourceforinformationaboutHayesproducts.TheBBSalsoprovidesadatabaseforthousandsofBBSintheU.S.Bestofall,itisfree.Unlessnotedotherwise,theresultsareobtainedbyusingthefollowing:Computer:MacSEwithMobiusTwoPageDisplaywith68030acceleratorModem:ATI9600etc/e(themodemissetasV.32withV.42bisenabled)OperatingSystem:System7.0CommunicationSoftware:ZTerm(Commportspeedsetto38400bps)FileTransferProtocol:ZmodemAllresultsarereportedbyZTerm.(IuseseveralcommunicationprogramsonbothIBMPCandMac.Allofthemshowtheaveragethroughputwhilefiletransferisinprogress,butZTermactuallyproducesareportafterthetransferiscompleted).̀V.42&MNP-4canimprovethroughputTheotherbenefitofV.42(orMNP4)isthatitcanimprovethroughput.Beforesendingthedatatoaremotesystem,amodemwithV.42(orMNP4)assemblesthedataintopacketsandduringthatprocessitisabletoreducethesizeofthedatabystrippingoutthestartandstopbits.Acharactertypicallytakesup1startbit,8databitsand1stopbitforatotalof10bits.WhentwomodemsestablishareliablelinkusingV.42orMNP4,thesendingmodemstripsthestartandstopbits(whichsubtracts20%ofthedata)andsendsthedatatotheotherend.Thereceivingmodemthenreinsertsthestartandstopbitsandpassthedatatotheremotecomputer.Therefore,evenwithoutcompressingthedatayoucanexpecttoseeasmuchas1150characterspersecondona9600bpsconnection.(Althoughthemodemsubtracts20%ofthedata,thespeedincreaseislessthan20%duetotheoverheadincurredbytheerrorcontrolprotocol.)Herearethetestresultsobtainedbydownlaodingthesamefile(1)withoutanyerrorcontrolprotocol,(2)withMNP-4,and(3)withV.42.Nodatacompressionprotocolisused.̀FilenameNoECMNP-4V.42̀------------------------------------------------------------------̀the-wave.txt935cps1151cps1128cps̀dayrpt.arc86310231002̀dayrpt.wks89810711052̀sunset.arc838971953̀sunset.pic90310801065̀text109k.arc90810851064̀text109k.txt93711501127AreMNP4andV.42useful?Absolutely.Anyonethathaseverusedastandardmodemcanappreciatethebenefitofanerror-freeconnection.Andtheincreaseindatathroughput,thoughmodest,isnothingtosneezeat.DataCompressionProtocols   	 p0.;   ЇBesideserrorcontrolprotocols,allcurrenthigh-speedmodemsalsosupportdatacompressionprotocols.Thatmeansthesendingmodemwillcompressthedataon-the-flyandthereceivingmodemwilldecompressthedatatoitsoriginalform.̀MNP-5andV.42bisTherearetwostandardsfordatacompressionprotocols,MNP-5andCCITTV.42bis.Somemodemsalsouseproprietarydatacompressionprotocols.Amodemcannotsupportdatacompressionwithoututilizinganerrorcontrolprotocol,althoughitispossibletohaveamodemthatonlysupportsanerrorcontrolprotocolbutnotanydatacompressionprotocol.AMNP-5modemrequiresMNP4errorcontrolprotocolandaV.42bismodemrequiresV.42errorcontrolprotocol.AlsonotethatalthoughV.42includeMNP-4,V.42bisdoesnotincludeMNP-5.However,virtuallyallhigh-speedmodemsthatsupportCCITTV.42bisalsoincorporateMNP-5.ThemaximumcompressionratiothataMNP-5modemcanachieveis2:1.Thatistosay,a9600bpsMNP-5modemcantransferdataupto19200bps.ThemaximumcompressionratioforaV.42bismodemis4:1.ThatiswhyallthoseV.32modemmanufacturersclaimthattheirmodemsprovidethroughputupto38400bps.AreMNP-5andV.42bisuseful?Don'tbefooledbytheclaim.Itisextremelyrare,ifever,thatyouwillbeabletotransferfilesat38400bps.Infact,V.42bisandMNP-5arenotveryusefulwhenyouaredownloadingfilesfromonlineservices.Why?Howwellthemodemcompressionworksdependsonwhatkindoffilesarebeingtransferred.Ingeneral,youwillbeabletoachievetwicethespeedfortransferringastandardtextfile(liketheoneyouarereadingrightnow).Decreasingby50%meansthatyoucandoublethethroughputonthelinesothata9600bpsmodemcaneffectivelytransmit19200bps.V.42bisandMNP-5modemcannotcompressafilewhichisalreadycompressedbysoftware.InthecaseofMNP-5,itwilleventrytocompressaprecompressedfileandactuallyexpandit,thusslowdownthefiletransfer!Herearethetestresultsobtainedbydownloadingthethreecompressedfilesusing(1)MNP-4withoutdatacompression,(2)MNP-5,(3)V.42withoutdatacompression,and(4)V.42bis.̀FilenameMNP-4MNP-5V.42V.42bis̀-------------------------------------------------------------------̀dayrpt.arc1023cps94610021010̀sunset.arc971935953950̀text109k.arc108598810641053IfyouhaveeverdownloadedfilesfromaBBSoronlineservice,youknowthatalmostallfilesareinacompressedformat.Therefore,youshouldonlyexpecttoseeanactualthroughputbetween950to1100cpsevenifyourV.32/V.42bismodemissupposedtoofferthroughput"upto"38400bps.MostPCfilesareintheZIPformat.Macintoshfilesaretypicallyin   	 p0.;   the.SIT(Stuffit)or.CPT(CompactPro)format.AmigafilesareusuallyintheZOO,ARCorLZHformat.NotethatGIFfilesarealsoinacompressedformat.̀CompressionbySoftwarevs.MNP-5/V.42bisThereareseveralreasonswhycompressionsoftwareprograms(suchasPKZIPorStuffit)aresuperiortoMNP-5orV.42bis.1.Compressedfilessavediskstoragespace.2.Compressionsoftwareprogramsaremoreversatile.Mostofthemalloẁyoutogroupseveralfilesinacompressedfilearchivetoensurèthatalltherelatedfilesgettransferredatthesametime.3.Softwarecompressionismoreefficientthanon-the-flymodem̀compression.Inthecaseofasmallfile,thismaynotmakemuch̀difference.Butthedifferencecanbesignificantwhenyouarètransferringlargefiles.̀FilenameSizeTimeThroughput̀-----------------------------------------------------------------̀the-wave.txt143579bytes43seconds3296cps̀dayrpt.arc8423bytes8seconds1010cps̀dayrpt.wks19712bytes8seconds2337cps̀sunset.arc5084bytes5seconds950cps̀sunset.pic16391bytes6seconds2643cps̀text109k.arc29775bytes28seconds1053cps̀text109k.txt111386bytes39seconds2822cpsAswecanseefromthetestresults,itisabout30%fastertotransferthecompressedfiletext109k.arcthantodownloadthetextfilewithV.42bis.HayesBBSdoesnotprovideacompressedversionforthefilethe-wave.txt.UsingPKZIP(forPC)andStuffit(forMacintosh),weobtainthefollowingresults:̀the-wave.zip:6812bytes(PKZIP)̀the-wave.sit:6081bytes(Stuffit)Assumingatransferspeedof1000cps,thecompressedfilecanbedownloadedin7seconds.That'ssixtimesfasterthandownloadingthetextfilewithV.42bis!Hereisanotherexample.SpiderIslandSoftwareBBS(714-730-5785)hasatestfilecalledOne-MinuteMax.ItisaMacintoshTIFFfile(filesize206,432bytes).AccordingtoSpiderIslandSoftware,thefilecanbedownloadedin56seconds(withaneffectivethroughputof3745cps)withaV.32/V.42bismodem.Theresultmayseemimpressiveatfirst.However,thefilecanbecompressedto6065bytes(withCompactPro)or7385bytes(withStuffit).Assumingatransferspeedof1000cps,itwouldonlytake6-8secondstotransfer.Again,itisseventoninetimesfasterthandownloadingthefilewithV.42bis.On-the-flymodemcompressiondoeshaveoneadvantage.Itismore   	 p0.;   convenient.Youcansendafilewithoutcompressingitfirstandtherecipientdoesnotneedtodecompressthefile.LocalFlowControlandDataBufferingTogetthemostfromamodemwithdatacompression,you'llwanttosenddatafromyourPCtothemodemasquicklyaspossible.Ifthemodemisidleandwaitingforthecomputertosenddata,youarenotgettingthemaximumperformancefromthemodem.Forexample,youhaveaV.32/V.42bismodemandyouwanttosendatextfiletoaremotesystemwhichalsohasaV.32/V.42bismodem.Let'sassumethemodemisabletosendthefileat20000bpsusingV.42bis.Ifyourcomputerissendingdatatoyourmodemat9600bps,yourmodemwillhavetostopandwaittoreceivedatafromyourcomputer.Togetthemaximumperformance,youwanttosetthecomputertosenddatatothemodemat38400bps(themaximumaV.32/V.42bismodemcanachieve).Sincethemodemcanonlysendthefiletotheothermodemat20000bps,itwillneverhavetowait.Herearethetestresultsfordownloadingthetextfilethe-wave.txtbysettingthecommunicationportatdifferentspeeds:̀the-wave.txt:946cps(modemportspeed9600bps)̀1885cps(modemportspeed19200bps)̀3296cps(modemportspeed38400bps)However,thereisanewproblem.Sinceyourcomputerissendingdatafasterthanthemodemcanhandle,thereneedstobesomewaysforthemodemtoaskthecomputertostopsendingdata.Otherwise,datalossissuretooccur.Thisiswherelocalflowcontrolcomesintoplay.Ahigh-speedmodemtypicallysupportstwokindsoflocalflowcontrol:hardwarehandshaking(CTS/RTS)andsoftwarehandshaking(XON/XOFF).Ofthetwo,hardwareflowcontrolisthepreferredmethod.Wehavementionedearlierthattherearethreelinksinvolvedwhenyouareconnectedtoaremotesystem:̀1.Thelinkbetweenyourcomputerandyourmodem̀2.Thelinkbetweenthemodems̀3.ThelinkbetweentheremotemodemandtheremotecomputerLocalflowcontrolisusedforthefirstandthirdlinks.Noticethatthefirstlinkmaynotusethesamekindofflowcontrolasthethirdlink.Hardwareflowcontrol(orhardwarehandshaking)worksbyalteringvoltagelevelsontheRTS(RequestToSend)andCTS(ClearToSend)signallinesattheRS232serialinterfacebetweenthemodemandthecomputer.CTSisusedbythemodemonthesendingendofatransmission.Whenthelocalmodemisreadytoreceivedata,itsendstheCTSsignaltothelocalcomputerandthecomputerstartstransferringdata.Ifthemodemisunabletoacceptthedataasfastasitisreceivedfromthecomputer,themodemwilldisabletheCTStoinformthecomputerthatthemodembufferisalmostfull(Ahigh-speedmodemtypicallycontainsa   	 p0.;   smallamountofRAMwhichisusedtoprovidedatabuffers).Thecomputerwillthensuspenddatatransfer.Oncethelocalmodemhasemptieditsbufferbytransmittingdatatotheremotemodem,itwillenableCTSagain.RTSisusedbythecomputeronthereceivingendofatransmission.Whenthecomputercannotacceptdataattherateatwhichthemodemispassingdata,itwilldisableRTS.ThecomputerenablesRTSagainwhenitisreadytoresumereceivingdatafromthemodem.Softwareflowcontrol(orsoftwarehandshaking)isachievedbyembeddingcontrolcharacterinthedatastream.XONandXOFFarethemostcommonlyusedcontrolcharacters.XONisalsoknownasControl-QorDC3(ASCII19)whileXOFFisknownasControl-SorDC1(ASCII17).TheuseofXONandXOFFduringdatatransfercancreateproblemwhenabinaryfilecontaintheControl-S(^S)characterasalegitimatepartofthedata.Donotusethismethodif^Sand^Qarepartofthetransmitteddata.BuyingaHigh-speedModem̀V.32andV.32bismodemsareclearlythestandardsofhigh-speedmodems̀today.YoushouldbuyaV.32oraV.32bismodemunless̀1.Yourapplicationrequiresahigh-speedmodemwithaproprietarỳmodulationprotocol.Inthiscase,youshouldconsideradual-modèmodemthatsupportboththeproprietaryprotocolandV.32(or̀V.32bis).̀2.YoucannotaffordaV.32modem.Inthiscase,youronlychoicefor     ahigh-speedmodemistheCompuComSpeedModemChamp.̀ShouldyoupaytheextraforaV.32bismodem?̀AV.32bismodemisfasterthanaV.32modembutitalsocostsmore.̀Shouldyoupaytheextraforthespeeddifference?Thatdependsontwòfactors:what'sthepricedifferenceandhowdoyouwanttoreachthèremotesystem.Ifthepricedifferenceis$50,IwouldbuytheV.32bis̀modem.Butwhatifthepricedifferenceis$200?̀AssumingtheremotesystemsupportV.32bis,aV.32bismodemwillpay    $ for   	 #!+   itselfratherquicklyifyouareplacinglongdistancecallsto     theremote   	 $`",   system.However,itmaybemorecost-effectiveforyouto     usesome   	 %(#-   packet-switchingnetworkstoreachtheremotesystemby     callingalocal   	 H&#.   number.AV.32bismodemwillbewastedsincenoneof    0 thepacket-switching   	 '$/   networkscurrentlysupportV.32bis.Infact,they    0 arejuststartingto   	 '%0   offer9600bpsaccessservice.PartIIIof"The     JoyofTelecomputing"   	 (H&1   providesacomprehensivediscussionofthe     issuesinvolved.   	 h)'2   ̀Shouldyoubuyamodemwithaproprietarymodulationprotocol?̀WiththeexceptionoftheCompuComSpeedModemChamp,itisgenerally    $ not   	 P-*7   agoodideatopurchaseamodemwhichonlysupportsaproprietarỳmodulationprotocol.Ifyouhavetoconnecttoamodemthatusesàproprietarymodulationprotocol,youshouldconsidergettingamodem̀thatsupportsdualmodulationprotocols(USRCourierDualStandard,   	 p0.;   ЀTelebit2500or3000,HayesUltra).̀ShouldyoubuytheSpeedModemChamp?ItcertainlycostsmuchlessthaǹeventheleastexpensivegenericV.32modeminthemarkettoday.̀AssumingthesystemsyouarecallingsupportbothV.32andthe    8" CompuCom   	 x    Champmodems,shouldyousavethemoneyandbuytheChamp?̀Unfortunately,thereisnoclear-cutanswertothequestion.The    $    	 x   answeragaindependsonhowyouaregoingtoreachtheremotesystems.    $ If   	 @   youwanttoreachtheremotesystemsviaapacket-switching     network,the   	 `		   CompuComChampmaynotbeagoodchoice.̀TheCompuComChampisgenerallynotsupportedbypacket-switching̀networks(TheonlycompanythatsupportstheCompuComChampis̀Connect-USA).Asaresult,youwillonlybeabletoconnectat2400    $ bps   	 H
   withthepacket-switchingnetworks.Youwouldbeforcedtoplacea    8" long   	    distancecallifyouwanttoconnectat9600bps.SeePartIIIof    8" "TheJoy   	    ofTelecomputing"forthevariousissuesinvolved.̀Shouldyoubuya2400bpsmodemwithV.42bis?̀Ifyouarethinkingofpurchasinga2400bpsmodemwithV.42bisdatàcompression,thinkagain.̀WehavementionedearlierthatV.42bisandMNP-5areuselessfor̀downloadingcompressedfiles.Thereisonemorereasonwhya2400bps̀withV.42bisisgenerallynotusefulwhenyouarecallingcommercial̀onlineservicesorBBS.̀OnlineservicesandBBSusuallyhaveseparatephonenumbersfor2400    $ bps   	 p   andhigh-speedmodems.MostofthemdonotsupportV.42bison     their2400bps   	 8   lines.Therefore,youwon'tbeabletomakea     connectionwithV.42bisif   	 X     youcalltheir2400bpsmodemlines.̀Couldn'tyoucalltheir9600bpslines?Well,notreally.Commercial̀onlineservices,aswellasmanybulletinboardsystems,typicallydònotallowyoutocalltheirhigh-speedmodemlineswitha2400bps̀modem.Youwon'tbeabletomakeaconnectionevenifyoutry.̀YoushouldseriouslyconsidertheCompuComSpeedModemChampinsteadof     a2400bpsmodemwithV.42bis.TheCompuComChampwillprobablygive    $ you   	 `" )   muchmoreforyourmoney(especiallyifyouneedtopaymorethan    8" $100for   	 (# *   theV.22bis/V.42bismodem).̀BewareoftheAds̀CurrentV.32modemstypicallysupportMNP2-5andV.42/V.42bis.    8" However,   	 '%0   therearestillsomeearliermodelsofV.32modemsinthe     marketwhich1.may   	 (H&1   notsupportanyerrorcontrolordatacompression    0 protocol(Hayes   	 h)'2   Smartmodem9600).̀2.maysupportMNP2-5butnotV.42/V.42bis.̀3.maysupportproprietarydatacompressionprotocol(MicrocomMNP-9).̀4.maysupportV.42butnotV.42bis(Prometheus).̀Whenamodemissaidtooffera38400bpsspeed(orthroughput),itmaymeanthat̀1.itisaV.32orV.32bismodemwithV.42bis   	 p0.;   Ѐ2.itisaV.32modemwithproprietarydatacompressionprotocol(somèMicrocommodems)̀3.itisahigh-speedmodemwithproprietarymodulationprotocoland̀V.42bis(U.S.RoboticsCourierHST)̀4.itisahigh-speedmodemwithproprietarymodulationprotocoland̀proprietarydatacompressionprotocol(CompuComChamp)̀Anadthatsays"USRmodem,38400bpsthroughput,V.42bis"doesnot    $ tell   	 x   usanythingexceptthatthemodemismadebyU.S.Robotics.It     couldbeany   	 @   oneofthethreeCouriermodems.Itcouldevenbea    0 Sportster9600.   	 `		   ̀Whenamodemissaidtooffera9600bpsspeed(orthroughput),itmaỳmeanseveralthings:̀1.itisaV.32modem̀2.itisahigh-speedmodemusingproprietarymodulationprotocol    $    	    (HayesV-seriesSmartmodem9600,Telebit1000,etc).̀3.itisa2400bpsmodemwithV.42bisdatacompression.̀4.itisa2400bpsmodemwith9600bpsfax̀5.itisa2400bpsmodembothV.42bisandfaxSettingUpSoftwareToWorkWithHigh-speedModems̀Gettingahigh-speedmodemisonlyhalfthebattle.Youwillneedto    $ get   	    ittoworkwithyourcommunicationsprogram.Mostcommunications̀programsstillcomewithsettingsconfiguredforstandard2400bps̀modems.̀Sinceall2400bpsmodemsareHayes-compatible,itisrelativelyeasy     tosetupthesoftware.Yousimplyinstallthesoftwareasifyouhad     aHayesmodem.Thesoftwareusuallywillworkflawlessly.Andyou    $    	 X     don'treallyhavetoworryaboutthingsliketheinitialization     string.   	  !   ̀Gettingahigh-speedmodemtoworkwithyoursoftwareisadifferent̀story.ThereisnolongeraHayesstandardthateveryonefollows.Herèaresomeofthereasonswhyyouneedtoknowhowtoconfigureyour̀high-speedmodemtoworkwithyourcommunicationsprogram.̀First,yourhigh-speedmodemmaynotbesupportedbyyoursoftware.̀Secondly,evenifyoursoftwaresupportsyourhigh-speedmodem,thèsoftwaremaynotbesetupproperly.̀Finally,evenifyoursoftwareissetupproperly,thesettingsmay    $ not   	 %(#-   workallthetimes.̀TheProperSoftwareSetup̀Whenwesaythatthesoftwareissetupproperly,wemeanthat̀1.themodemisinitializedproperlybythecommunicationssoftware,    $ and   	 +h)5   2.thesettingsofyoursoftwarematchthoseofthemodem̀Whatistheproperwaytoinitializeahigh-speedmodem?Ingeneral,̀yourmodemneedstobeinitializedto:̀*EnableV.42bisDataCompression   	 p0.;   Ѐ*Enablehardwareflowcontrol̀*HandletheDTRandCDsignalsproperly(byadding&C1&D2tothe    $    	      modeminitializationstring)̀We'llusetheATI9600etc/emodemasanexampleforourdiscussions̀below.TheinitializationstringdescribedhereisfortheATImodem̀only.Refertoyourmodemmanualfortheequivalentinitializatioǹstringforyourmodem.̀TheATImodemissupportedbytwopopularcommunicationsprograms:̀QmodemandHyperAccess5.Qmodeminitializesthemodemandalsòconfiguresitselftousehardwareflowcontrol.HyperAccess5alsòinitializesthemodemproperly,howeveritdoesnotconfigureitself    $ to   	 `	   usehardwareflowcontrol.̀Allmodemscomewithdefaultsettingspre-configuredfromthefactory.̀ManyV.32high-speedmodemsarepresettouseV.42bisandhardware    $ flow   	    controlwhentheyareturnedon.Thisoptimalconfiguration     enablesthe   	 H
   modemtoautomaticallynegotiateaconnectionwitheither     anotherV.32modem   	 h   supportingV.42bisorMNPprotocols(orevena     standardmodem).   	 0   ̀Interestinglyenough,notallhigh-speedmodemsareconfiguredthis    $ way.   	 h   TheATI9600etc/emodem,forexample,ispresettouseV.32     withouterror   	 0   controlordatacompressionatpower-on.(Why?Good    0 question.)   	 P   ̀Asaresult,yourcommunicationsprogramneedstoissuethe    8"    	    appropriateinitializationstring(AT&F2)tosetuptheATImodemto    8" useV.32   	 P   withV.42bisandhardwareflowcontrol.̀Thereisanotherchangerequired.Andithastodowiththeparameters̀controllinghowthemodemdealswithtwooftheRS232signals:DTR    $    	 p   (DataTerminalReady)andCD(CarrierDetect).̀CDisasignalgeneratedbythemodemwhichisusedtoindicateits̀connectionstatus.DTRisasignalgeneratedbyyourcomputer.DTRis̀usedtoenablethemodemtoacceptcommandsfromyourcommunications̀program,itisalsousedbymostmodemstodeterminewhento    8"    	 x $   disconnectacall.̀ThefactorydefaultsettingforDTRtellsthemodemtoignorechange    $ in   	  x'   DTR(&D0),andthesettingforCDforcesCDalwayson(&C0).Thesèspecificsettingsarerequiredbysomededicateddumbterminalsin    $    	 `" )   ordertocommunicatewiththemodem.(Virtuallyallmodemsuse&C0&D0    $ as   	 (# *   thedefaultsetting.)However,thesesettingswilloftencause     problemswhen   	 #!+   hangingupthephonelinesorproduceanerrormessage     whichsaysthe   	 $`",   modemisonlinewhenitisnot.̀MostcommunicationssoftwareprogramsexpectthemodemtofollowDTR    $ and   	 '$/   expectsCDtofollowcarrier.&C1&D2settheparametersforthe     modemto   	 '%0   handletheDTRandCDsignalsasexpectedbymost    0 communicationsprograms.   	 (H&1   ̀Therefore,theproperinitializationstringtousefortheATImodem̀shouldbeAT&F2&C1&D2.̀DoesYourSoftwareInitializetheModemProperly?̀Let'stakealookattheinitializationstringsusedbyQmodemand̀HyperAccess5fortheATI9600etc/emodem.   	 p0.;   ЀHyperAccess5usethefollowinginitializationstring̀AT&F2E1V1L0Q0W2X4&C1&D2S11=55̀Thisstringislongerthantheonewesuggest.Butdoesitdomore?̀Actuallyitdoesn't.Manyofthecommandsinthestringareredundant     ornotnecessary.OnlyAT&F2&C1&D2arecrucial.̀Fourofthecommands-E1,V1,Q0andX4-areredundantsincethey    $ are   	 @   duplicationsofthefactorydefaultsettings.(Checkyourmodem     manualtofind   	 `		   outwhattheymean.Sinceyouwouldmostlikelyneedto     readitsooneror   	 (

   later,youmightaswellgetstartednow.)̀L0doesnotapplytotheATImodem.L0normallyisusedtosetmodem̀speakervolumetothelowestlevel.However,theATI9600etc/emodem̀doesnotrespondtotheL0command.Unlikemostmodems,theATImodem̀hasaslidevolumecontrolontherightsideforadjustingthevolumèlevel.̀Theothertwocommands(W2andS11=55)arenotredundant,buttheyarènotnecessary.̀W2setsthemodemtoreportNegotiationresultcodesinsinglelinèformatinsteadofthedefaultthreelineformat(W1).̀Threelineformat:Singlelineformat:̀-----------------------------------̀CARRIER9600CONNECT9600/LAP-M̀PROTOCOL:LAP-M̀CONNECT38400̀S11=55(defaultis95)setsthemodemtodialatafasterspeedthan    $ the   	 X     factorysetting.̀Despitethefactthatitsinitializationstringcontainssome    8" redundant   	 X#   commands,HyperAccess5doesproperlyinitializetheATI     modem.   	 x $   ̀AlthoughHyperAccess5willinitializethemodemwiththestringeverỳtimeyoudialaremotesystem,theprogramdoesnotchangethefactorỳdefaultsettingsfortheATImodem(whichisV.32withouterror    8" control   	 !@(   ordatacompression).Everytimeyouturnthemodemoffand     backon,the   	 `" )   modemwillreverttoitsfactorydefaults.̀UnlikeHyperAccess5(andothercommunicationsprograms),Qmodemdoes     itinadifferentway.Itactuallyreplacestheoldfactorydefault    $    	 %(#-   setting(AT&F)oftheATImodemwithanewdefaultconfiguration    8"    	 H&#.   (AT&F2&C1&D2).̀WhenyoufirstinstallQmodemtoworkwithanATI9600etc/emodem,    $ the   	 (H&1   programsendsthefollowingtwostringstothemodem(makesure     themodemis   	 h)'2   connectedtoyourPCandisturnedon):̀AT&F2^M̀AT&C1&D2&W^M̀ThefirststringsetsthemodemasV.32withV.42bisenabled,hardwarèflowcontrolenabled(amongotherthings).Notethat^Misequivalent     tosendingaCarriageReturntothemodem.   	 p0.;   ЀThesecondstringchangesthefactorysettingsoftheCDandDTR̀(&C0&D0)andthenwrite(&W)allthenewactiveconfigurationsettings̀tothenonvolatilememoryofthemodem.Thenewsettingsarenow    $    	    storedbythemodemandbecomethenewdefaultconfigurationwhenthe    $    	 X   modemispoweredon(orwhenitreceivedtheATZcommand).̀Thus,Qmodemsimplysendstheinitializationstring"ATZ^M"(which̀resetsthemodemtoitsdefaultstate,nowAT&F2&C1&D2)tothemodem̀wheneveryouloadtheprogram.̀Althoughthetwoprogramsusedifferenttechniques,theresultisthèsame.ThemodemisinitializedasV.32/V.42biswithhardwarefloẁcontrolenabled,whichisnormallytheoptimumsetting.̀DoesYourSoftwareConfigureItselftoMatchtheModemSettings?̀Besidessendingtherightinitializationstringtothemodem,thècommunicationssoftwarewillalsoneedtomatchthemodemsetting.̀Specifically,thecommunicationssoftwareshouldalsousehardware    $ flow   	 0   controlsincethemodemisinitializedwithhardwareflowcontrol̀enabled.̀Onewouldexpectthatwhenasoftwareinitializesthemodemtousèhardwareflowcontrol,thesoftwareitselfwouldalsousehardware    $ flow   	    control.Butitisnotalwaystrue.Aswementionedearlier,     HyperAccess5   	    initializesthemodemwithhardwareflowcontrol     enabled,butexpectyouto   	 P   changetheflowcontrolsettingsineach     individualdialingentry.   	 p   ̀WhyYouMayNeedtoChangetheInitializationString̀Ingeneral,thestringAT&F2&C1&D2shouldworkwithoutanyproblem.    $ But   	 X     thereisnoguaranteethatitwillalwayswork.Whenitdoesnot    8" work,   	  !   you'llnormallyneedtochangetheinitializationstringto     solvethe   	 "   problems.̀Hereareafewreasonswhytheinitializationstringusedbyyour̀communicationsprogrammaynotwork:̀1.Thesettingsneedadjustmentstoworkwiththesystemyouarècalling.̀Case1:WhenIcalledtheHayesBBS,themodemwouldabortand    $    	 #!+   failedtomakeaconnection.Itturnedoutthatthedefaultsetting    8" (30   	 $`",   seconds)oftheS7registerisnotlongenoughfortheATI     modemtomakea   	 %(#-   connectionwiththeHayesUltra96modemonthe     otherend.   	 H&#.   ̀Solution:ToestablishaconnectiontotheHayesBBS,Ineedtoadd̀"S7=60"tothemodeminitializationstringandalsochangethèsettinginthecommunicationssoftwaretowait60secondsforàconnection.̀ByinitializingthemodemwiththestringAT&F2&C1&D2S7=60,Iwas̀abletoconnectwithoutanyproblem.(Thedefaultsettingforthe    $    	 ,0*6   S7registerisnotuniversal,theHayesUltraandPractical         8"    	 P-*7   Peripheraluse50secondsasthedefaultvalue.)Notethatthereis    8"    	 .+8   nothingspecialaboutthenumber60.Inmyparticularcase,any     number   	 .,9   largerhan45willwork.   	 p0.;   ЀCase2:WhenIcallasystemthatusestheTelebitT1600modems,ÌcannotmakeaconnectioniftheATImodemissettouseV.42bisor̀MNP-5.TheATImodemwillonlyconnectreliablywhenitissetto    $    	    useMNP-4.̀Solution:Toconnectsuccessfully,Ihavetosetupthemodemas    $    	 @   V.32withMNP-4bysendingthestringAT&F1&U0totheATImodem.    8" (AT&F1   	    setstheATImodemasV.32withMNP-5,&U0turnsoffdatàcompression.)̀2.Yourcommunicationsoftwaremaynotbecompatiblewiththesetting.̀Forexample,AmericaOnlineimplementedanerror-correctingscheme     inthesoftware(boththePCandtheMacversions)whichisnot̀compatiblewiththemodem'serrorcorrectionprotocol.̀Solution:TouseAmericaOnline,youneedtoturnofferrorcontrol̀onthemodem.AT&FconfigurestheATImodemasV.32withouterror̀control.̀3.Yourcomputerhardwaremaynotworkwiththesetting.AsImentioǹearlier,youneedaproperlywiredcablefortheMactouse    8"     $    	    hardwareflowcontrol.Ifyoudonothavetherightcableorif     yourMac   	 h   simplywon'tworkwiththecable,youwillneedtouse     softwareflow   	 0   control.(&K4tellstheATImodemtousesoftware    0 flowcontrol.)   	 P   ̀Solution:TousetheATImodeminV.32/V.42bismodewithmyMac,ÌneedtodisablehardwareflowcontrolanduseXON/XOFFsoftware    $    	 P   flowcontrolinstead.ThestringAT&F2&K4&C1&D2S7=60setsupthe    8" modem   	 p   properly(again,S7=60isforcallingtheHayesBBS).̀4.Youmayneedtochangethesettingtoachievebetterperformance.    $    	 p   ItisadvisablethatyouturnoffMNP-5whiledownloading         8"    	 8   pre-compressedfilesfromaremotesystemthathasaMNP-5modem.    8" You   	 X     caninitializetheATImodemtoturnoffMNP-5datacompression     withthe   	  !   stringAT&F1&U0.̀Again,theinitializationstringusedhereisfortheATImodemonly.     Ifyouuseadifferentmodem,youwouldneedtocheckwiththemodem    $    	  &   manualtofindouttheequivalentcommandstouse.̀EditingtheInitializationString̀Iftheinitializationstringprovidedbyyoursoftwaredoesnotwork    $ (or   	 $`",   ifyoursoftwaredoesnotsupportyourmodematall),you'llneed    8" toedit   	 %(#-   theinitializationstringinyourcommunicationsprogram.̀Themodeminitializationstringconsistsofaseriesofcommands    $    	 '%0   (calledtheATcommands).Theycanbedividedintothreegroups:̀1.Acapitalcharacterfollowedbyadigit.Forexample,M1.̀2.Anampersand&andacapitalcharacterfollowedbyadigit.For̀example,&M1.NotethatM1isdifferentfrom&M1.̀3.Sr=nwhere"r"isthenumberoftheregistertobechangedand"n"     isthenewvaluethatisbeingassigned.Forexample,S7=60.̀Therearesomeothercharactersthatmayalsoappearinthemodem̀initializationstring.Thesecharactersnormallyshouldnotbe    8" changed.   	 /P-:      	 p0.;   ЀATtellsthemodemthatmodemcommandsfollow.̀Zresetsthemodemtodefaultstatè~makesyoursoftwarepauseforhalfasecond.Youcanusèmorethanone~inarow.Forexample,~~~~tellsthèsoftwaretopausetwoseconds.̀^MsendstheterminatingCarriageReturncharactertothèmodem.Thisisacontrolcodethatmostcommunicatioǹsoftwaretranslateasa"carriagereturn."̀Let'sassumethattheappropriateinitializationstringtouseis̀AT&F2&C1&D2S7=60(fortheATImodem).You'llneedtoreplacethis    $    	 H
   stringwiththeoneprovidedbyyourcommunicationssoftware.̀Ifyoursoftwaredoesnotsupportyourmodem,youcaninstallthèprogrambytellingitthatyouhaveaHayesmodem.Afterthèinstallation,you'llsimplyedittheinitializationstringwiththèappropriateone.Pleasemakesureyoudonotdeleteany~or^M.̀Herearesomeexamples,̀1.TochangethestringprovidedbyProcommPlus̀ATE1S7=60S11=60V1X1Q0S0=0^M̀Usethestring̀AT&F2&C1&D2S7=60^M̀2.ToeditthestringusedbyTelix̀ATZ^M~~~ATS7=45S0=0V1X4^M̀changeittòATZ^M~~~AT&F2&C1&D2S7=60^M̀3.ToreplacetheinitializationstringprovidedbyZTerm(Macintosh)̀ATE1M1V1^M̀usethefollowingstring̀AT&F2&C1&D2S7=60^M̀MatchSoftwareSettingsTotheModemSettings̀Besidesusingtherightinitializationstring,youalsoneedtomakèsurethatthesettingsinyourcommunicationsprogrammatchthoseof    $ the   	 *(4   modem.̀Speedsetting̀Ifyouhaveamodemthatsupportsdatacompression.Youwanttomakèsurethatthespeedsettingfortheentriesinyourdialingdirectory     isthemaximumthroughput.Herearethegeneralrulesofthumb:   	 p0.;   ЇForaV.32bis/V.42bismodem,setspeedto38400or57600bps(check    $ your   	 X      modemmanual).̀ForaV.32/V.42bismodem,setspeedto38400bps.̀ForaV.32/MNP-5modem,setspeedto19200bps.̀ForaV.22bis/V.42bismodem,setspeedto9600bps.̀ForaV.22bis/MNP-5modem,setspeedto4800bps.̀Note:Yourcomputermaynotbefastenoughtoworkreliablyat38400    $ or   	 x   57600bps.Also,thecommunicationsprogramsyouusemaynot     supportspeed   	 @   higherthan19200bps.̀Hardwareflowcontrol̀Notethatyouwillneedtoconfigureyoursoftwaretousehardwarèhandshakingifthemodemisinitializedtousehardwareflowcontrol.̀DialingTime-outValuèIndependentfromyourmodemsetting,yoursoftwaremayalsoimposeàlimitonhowlongitwillwaitforaconnection.IfyouinitializethèmodemwiththecommandS7=60,you'llneedtochangethetime-outvaluèusedbyyoursoftwareto60secondsaccordingly.ConfiguringPopularCommunicationsSoftwaretoWorkwithHigh-speedModems̀Belowarebriefinstructionsforconfiguringsomepopularcommunications̀programstoworkwithahigh-speedmodem.TheparticularinitializatioǹstringisfortheATI9600etc/emodem.ItisassumedthatthèappropriateinitializationstringtouseisAT&F2&C1&D2S7=60.̀Makesureyousavethechangesyoumake.	   	 "   