Fallback Modes When On-Line #F | Multitech MT2834BA, MT1432BA

Chapter 5 - Command Mode

Fallback Modes When On-Line #F

If line conditions deteriorate, the modem automatically drops its transmission speed (“fallback”). The #F command controls the different ways the modem falls back. During operation, if the error rate becomes too great, the modem performs a retrain. If after the retrain, the error rate is still too high for 33600 bps (19200 bps for 1932 models, 14400 bps for 1432 models) operation, the modem initiates a retrain at 4800 bps. If after the first retrain the modem returns on line at 33600 bps (14400 bps for 1432 models, 9600 for 932 models), the modem then starts a counter and a timer. If three retrains occur within a two minute period, the modem falls back to 4800 bps.

Entering AT#F0 (or AT#F) allows no fallback when on-line.

AT#F1 allows the modem to fallback (based on the error rate or if three retrains have occurred within a two minute period) from:

2834 Series: 33.6K to 31.2K to 28.8K to 26.4K to 24K to 21.6K to 19.2K to 16.8K to 14.4K to 12K to 9.6K to 4.8K bps.

1432 Series: 14.4K to 12K to 9.6K to 4.8K bps.

932 Series: 9.6K to 4.8K bps.

The AT#F2 command enables incremental fall back, but also enables incremental fall forward if the phone line improves. AT#F2 is the factory default setting.

Enable/Disable Lowspeed Fast Connect $FC (2834 Series only)

Entering AT$FC0&W0<CR> sets up the data pump so that it will not transmit a 5 second 2100 Hz signal. Entering AT$FC0&W0<CR> allows the modem to transmit a 5 second 2100 Hz signal and is the factory default.

Cleardown at Disconnect &CD (2834 Series only)

The &CD command is used for control of cleardown at disconnect in V.32, V.32bis, V.34 and V.34 enhanced modes.

A cleardown usually adds 1-2 seconds to the time it takes for the modem to go on-hook after a disconnect. A cleardown makes a disconnect by the remote modem easier to detect and a subsequent re-connection more likely. Enter AT&CD0&W0<CR> to execute a cleardown at disconnect (default); and enter AT&CD1&W0<CR> to disable the cleardown function.

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Multitech MT2834BA, MT1432BA Fallback Modes When On-Line #F, Enable/Disable Lowspeed Fast Connect $FC 2834 Series only

Contents

User Guide Record of Revisions User Guide Contents Registers Command ModeCallback Security and Remote Configuration Manual Dial and Automatic Answer Appendixes Modem TestingDIP-Switch Settings Warranty, Service and Tech SupportPage Introduction and Description Introduction How To Use This Manual DIP-Switches AT Command Mode OperationCallback and Remote Configuration Testing Your Modem 3 932 Series Features Modem Features1 2834 Series Features 2 1432 Series Features Fax Features Technical Specifications Introduction and Description Mode of OperationIntelligent Features Command Buffer Transmit Level Fax Carrier FrequenciesCarrier Frequencies Carrier Frequencies 300 bps Bell Standard Operating Temperature ConnectorsDiagnostics Indicators Models Only PowerModem LED Indicators Controls on PC Board MultiModemBA User Guide Installation and Connection Unpacking MT2834BA shown What is in Your Modem Package? Installation Procedure InstallationSafety Warnings MultiModemBA/BAI Connections Loading Trio DataFAX Software MultiModemBA User Guide Is Your Modem Ready for Use? MultiModemBA User Guide Software Configuration and Modem Basics How Can You Identify Your Uart Type? Serial Port Limitations 16550 Uart and Windows Configuring Your SoftwareConfiguring Software for Your Modem Software Configuration Other Parameters Changing Default ParametersPC Initialization Strings Terminal Emulation Configuring Software for Your ComputerConfiguring Software for the Remote System Macintosh Initialization AT &F S0=0 X4 &E14 M When to Disable Data CompressionDisabling Error Correction File Transfer Protocols Simple Operations Answer/Originate Voice/Data Toggle SwitchModem Basics MultiModemBA User Guide Manual Dial and Automatic Answer Dialing/On-Line/Answering Manual Dial and Automatic Answer Manual Call OriginationAutomatic Answering Handshaking Details Manual Answering Call Termination Abort Timer MultiModemBA User Guide Command Mode AT Command Editing Functional Modes Command Mode Summary of AT Commands Flow Control Disabled Normal ModeAuto-Reliable Mode Reliable Mode Callback Security Enable/Disable Enable/Disable Reading Line Probe From DSP during handshakeDisplay of Signal Strength Information Passwords for Callback Phone Numbers Multi-Tech Result Codes Series Result Codes MultiModemBA User Guide Standard AT Result Codes Series Dialing a Stored Number N Dialing Commands Dialing Action CommandsDial Command D Continuous Redial not used in BAI a or Set Pulse Dial Ratios &P Dial Modifier CommandsVoice/Data Dialing $VD Pulse or Tone Dial P T Long Space Disconnect Y Return to Command Mode After Dial Command ExecutionReverse the Mode of Operation R Automatic Pauses in Dialing Quiet Answer @ Calling Card Detect Tones $ Listing Numbers Stored in Memory L Phone Number Memory CommandsStoring Phone Numbers D...N Number Linking NN Modem Reset Z Configuration and Default Storage CommandsLoading Factory Defaults &F Synchronous Transmit Clock Select &X Async/Sync Mode Switching &MUnix Uucp Spoofing $SP Result Codes Multi-Tech or Standard AT &Q Command Response Result Code CommandsEcho Command Mode Characters E Result Codes Enable/Disable and No Response Answer Q Result Codes Basic and Extended and Call Progress Selection Bell/V.21 Tone Phone Line Conditioning CommandsEnable/Disable Trelis Coded Modulation #T Guard Tones Not Used in BAI Models &G Cleardown at Disconnect &CD 2834 Series only Fallback Modes When On-Line #FEnable/Disable Lowspeed Fast Connect $FC 2834 Series only Auto Speed Detect #A CTS Control &R 7 RS-232C Interface Control CommandsCarrier Detect Control &C Data Terminal Ready Control &D DSR/CD Interaction Control &SF Data Set Ready Control &SCTS/RTS Interaction Control &RF Reliable Mode &E2 Error Correction CommandsNormal Mode &E0 Auto-Reliable Mode &E1 Auto-Reliable Buffering $A Mode Select #LOriginate Mode Answer Mode Retransmit Count $R Enable/Disable Auto Reliable Fallback Character $FError Correction/300bps $E Xon/Xoff Flow Control &E5 Flow Control CommandsHardware Flow Control &E4 Hewlett-Packard ENQ/ACK Pacing &E9 Xon/Xoff Pass-Through &E7Send Xon/Xoff Characters #X Parity Selection #P Normal Mode Modem Flow Control On &E11Terminal/Computer Initiated Pacing &E13 Maximum Block Size &BS Enq/Ack Pacing Commands Normal/Auto-Reliable/Reliable Mode CommandsXon/Xoff Pass-Through Commands Modem Baud Rate $MB Speed Conversion CommandsSpeed Conversion $BA Command Mode Series Serial Port Baud Rate $SB Immediate Action Commands Off Hook H Listing On-Line Diagnostics L8 Exiting Command Mode, Going Back On-Line O Line Probe Commands 2834 Series onlyForce Answer Mode a MultiModemBA User Guide Registers Return Character Number of Rings Until Modem AnswersRings Which Have Occurred Escape Code Character Wait Time for Dial Tone Time for Carrier Abort TimerLine Feed Character Backspace Character S11 Tone Dialing Tone Spacing and Duration S10 Carrier Loss Disconnect Delay TimeS13 Remote Configuration Escape Character Carrier Detect Response Time S24 PBX/CBX Disconnect Drop Time for DSR/CTS/CD S15 Callback Time DelayS16 Callback Attempts S17 Changing Break Time S32 Time Elapse for Escape Sequence S26 Failed Password AttemptsS29 Local Inactivity Timer S30 Inactivity Timer S48 Program V.34bis Connect Speeds 2834 Series only S36 Time Between DTR Inactive and Modem Off-HookS37 Time Between DTR Active and Modem On-Hook Examples of Reading Values Reading and Assigning S-Register ValuesExamples of Assigning Values AT Command and S-Register Summary MultiModemBA User Guide Callback Security and Remote Configuration Callback Feature Description To change your Remote Configuration feature status Remote Configuration DescriptionCallback Security and Remote Configuration AT#CBN1xxxxxxxxxxCR To set parity of the password/message promptAT#CBN0xxxxxxxxxxCR Callback Operational Sequence Procedures Remote Configuration Operation Procedures StepProcedure Remote Configuration Procedures Change Login Password Remote Configuration and Callback Security AT CommandsAssign Passwords for Callback Phone Numbers #CBN Callback Security Enable/Disable Erase Callback Phone Number #RDNxx Erase Callback Password Remote Configuration/Callback Security S-Registers MultiModemBA User Guide Modem Testing Introduction Local Analog Loopback Test/V.54 Loop Modem Testing 100 Digital Loopback Test/V.54 Loop 2 Local/Manual 101 Digital Loopback Test/V.54 Loop 2 Remote/Automatic 4A. Back-to-Back Test Cabling Back-to-Back Test Local Analog Loopback Test Synchronous Mode Synchronous Mode Testing Synchronous Mode Digital Loopback Test local/manual 104 Digital Loopback Test Local/Manual Synchronous Mode Synchronous Mode Digital Loopback Test remote/automatic 105 Digital Loopback Test Remote/Automatic Synchronous Mode MultiModemBA User Guide 106 DIP-Switch Settings PC Board 108 109 DIP-Switch Option SettingsDIP-Switch Settings 110 Switch #4 AS/400 Mode Synchronous Mode/Leased Line/Dial-UP932 Series 111 112 113 114 Switch #16 Reserved for Future UseMultiModemBA User Guide Series 115 Speaker Volume ControlRecording Option Configurations Switch Function Position Effect 116 DIP Switches #13-14DIP Switches #15-16 Warranty, Service and Tech Support 118 Limited WarrantyOn-line Warranty Registration Recording Modem Information ServiceWarranty, Service and Tech Support Tech Support To Download a file Multi-Tech BBSTo log on to the Multi-Tech BBS About Multi-Tech’s Internet Presence Using FlashPro to Upgrade Modem FirmwareAbout the Multi-Tech Fax-Back Service Upgrading the MultiModem 122 About Ordering AccessoriesSupplyNet Online Ordering Instructions Appendixes 124 Appendix a TroubleshootingNone of the LEDs Light When the Modem Is On Modem Does Not Respond to Commands 125 Appendix a Troubleshooting 126 Modem Dials But Cannot Make a Connection 127 Modem Cannot Connect When AnsweringModem Disconnects While On-line File Transfer Is Slower Than It Should Be 128 Am Losing DataAm Getting Garbage Characters on the Monitor 129 Appendix B Ascii Conversion Chart 130 Appendix C Dial Pulse and Tone-Dial FrequenciesDial Pulses Tone Dial Frequencies #An Appendix D AT Command SummaryCommand Values Description $An SN d BS n$BA n CD n 133 $EBn#Fn $Fn 134 $Hn#Ln $MBn Sr=n NdNe$Rn RFn #Tn $SBnSFn $SPn 137 $VDn#Xn +++ATCR Callback Security/Remote Configuration Command Summary 25bis Commands Password Command Summary 140 Appendix E DIP-Switch SummaryAsynchronous Mode 141 Synchronous ModeAppendix E DIP-Switch Summary 142 Appendix F S-Register Summary S34 S29S30 S32 145 Appendix G Result Code SummaryAppendix G Result Code Summary Terse Digit Verbose Words Effect 146 Appendix H V.25bis Operation Delayed and Forbidden NumbersAppendix H V.25bis Operation 25bis Operation 148 25bis DIP-Switches25bis Set-Up and Initialization 149 25bis Mode AT Commands25bis Responses Result Codes Dial Phone Number Provided CRN Command 25bis AT CommandsEnable/Disable V.25bis Mode $V Command Change Serial Baud Rate CSP Command DTR Dialing $D Command Listing Delayed Phone Numbers RLD CommandListing Forbidden Phone Number RLF Command Disregard or Connect to Incoming Calls DIC or CIC Command Austria ITU V.25bis Country Specific InformationItaly Switzerland 153 Appendix H V.25bis Operation FranceBelgium Singapore Figure I-1. RS232 Cable IBM PC Appendix I MultiModemBA Cables Figure I-2. MAC Cable 155 Appendix J RS-232C Interface Specifications 156 Appendix J RS-232C Interface SpecificationsSignal Function Assignment Circuit Source Pin Designation Eia Clear To Send Pin 5, CTS CB Signal Ground Pin 7, SG ABReceived Data Pin 3, RD BB Request To Send Pin 4, RTS CA Receive Clock Pin 17, RC DD Ring Indicator Pin 22, RI CETest Voltage Pin 9 Transmit Clock Pin 15, TC DB 159 Terminal Busy Out of Service Pin 25, OOSExternal Transmit Clock Pin 24, XTC European Directives User Guide Statement EMC, Safety and Terminal Directive ComplianceInternational Modem Restrictions New Zealand Telecom Warning Notice 161 FCC Regulations for Telephone Line InterconnectionAppendix K Regulatory Information Industry Canada Canadian Limitations NoticeClass a Statement FCC Part 163 Index 164 Functional Description of RS232C SIG 165 166