Multi-Tech Systems MT4X56USB Local Digital Loopback Test V.54 Loop, Local digital loopback test

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Chapter 6 - Troubleshooting

Local Digital Loopback Test (V.54 Loop 2)

The local digital loopback test is identical to the remote digital loopback test with one exception. Instead of using your modem to signal a remote modem to place itself in digital loopback mode, your modem is placed in digital loopback mode while the remote modem is not. Data is entered and transmitted from the remote modem, sent across the phone line to your modem, and looped back to the remote modem.

AT&T3

UUUUUUUUU

OK

UUUUU

Digital Analog

Analog Digital

Computer or Terminal

Local MultiModemUSB

Remote MultiModemUSB

Computer or Terminal

Figure 6-3. Local digital loopback test

Test Procedure

1.Open your communications software and go into terminal mode. Type AT and press ENTER; you should get an OK message. Type AT\N and press ENTER to disable error correction.

2.Dial the remote modem and establish your online connection.

3.Type the escape sequence +++AT and press ENTER to bring your modem into online command mode.

4.Type AT&T3 and press ENTER. Once you receive an OK message from your modem (if responses are enabled), your modem is placed in digital loopback mode.

5.Have someone enter data from the remote keyboard. For this test, typing multiple uppercase U characters is a good way to send an alternating test pattern of binary ones and zeros. The data received by your modem enters its analog receiver, is converted to digital data, is reconverted into analog, and then is transmitted back to the remote modem. Your modem passes this test if the data received on the remote monitor is the same as the data entered from the remote keyboard.

6.To exit the test, type the escape sequence +++AT and press ENTER. This puts the modem in online command mode. The modem should respond with an OK message. If you wish to stay on line with the remote modem for normal data transmission, type AT&T and press ENTER to exit the test, then type ATO and press ENTER to return on line. If you wish to terminate the call, type ATH and press ENTER to hang up.

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Contents User Guide MultiModemUSB Model MT4X56USBTrademarks User GuideRecord of Revisions PatentsContents Glossary of Terms Index Introduction and Description Features IntroductionMultiModemUSB User Guide Introduction and Description Technical SpecificationsInstallation Preview of this GuideRelated Documentation System Front PanelModem Ports Ports 1, 2, 3, HubPower Connector RJ-ll Modem ConnectorUSB Type a Upstream Connector USB Type B Downstream ConnectorInstallation Unpacking Safety Warning TelecomCabling your MT4X56USB InstallationMT4X56USB Software Loading and Configuration System USB Support Loading your Driver SoftwareMT4X56USB Drivers for Windows Software Loading and Configuration Uninstalling MultiModemUSB in Windows MT4X56USB Drivers for Windows Uninstalling MultiModemUSB in Windows MT4X56USB Drivers for Windows NT MultiModemUSB Drivers Install dialog box displays Click NextUninstalling MultiModemUSB in Windows NT Select Add/Remove ProgramsAdd/Remove MT4X56USB Drivers for Windows Click Finish Software Loading and Configuration Select Add/Remove Hardware Click Start Settings Control Panel Modems Installing Your V.90 ModemsRead Carefully Software Loading and Configuration MT4X56USB Click Start Settings Control Panel Phone and Modems option Installing Your V.90 Modems WindowsMT4X56USB Software Loading and Configuration Windows 95/98 Configuration Utility MT4X56USB Windows NT 4.0/2000 Configuration Utility MT4X56USB MT4X56USB AT Commands, S-Registers and Result Codes Answer AT Command SummaryCommand Enter Key Repeat Last CommandAT Commands, S-Registers and Result Codes Modulation Handshake Return Online to Data ModeResult Codes Enable/Disable Information RequestResult Code Format Modem ResetLoad Factory Settings Tone DialingDisplay Current Settings Communications ModeAsynchronous Communications Mode Test Commands\An Select Maximum MNP Block Size Store Current ConfigurationSelect Stored Configuration for Hard Reset Command &Zy=x Store Dialing Command\Qn Flow Control Selection \Nn Error Correction Mode Selection\Tn Inactivity Timer \Kn Break ControlCommand #S=x Store Setup Password Command %DCn AT Command ControlCommand %En Fallback and Fall Forward Control Enter Setup PasswordCommand %%%ATCRRemote Configuration Escape Sequence Command +++ATCR Escape SequenceRegisters Register Unit Range Default DescriptionUpstream data rates S38Terse Verbose Description Result CodesFor more information on scripting, click the Help button Remote Configuration Remote Configuration Procedure SetupChanging the Setup Password Remote Configuration Commands Remote Configuration and ManagementChanging the Remote Escape Character MT4X56USB Troubleshooting None of the Indicators Light Modem Does Not Respond to CommandsModem Dials But Cannot Connect Modem Disconnects While Online TroubleshootingFax and Data Software Can’t Run at the Same Time Modem Cannot Connect When AnsweringLoopback Tests Modem Doesn’t Work with Caller IDLocal Analog Loopback Test V.54 Loop Test procedureRemote digital loopback test Remote Digital Loopback Test V.54 LoopLocal digital loopback test Local Digital Loopback Test V.54 LoopDouble-click the Universal Serial Bus Controller icon Windows 95/98 TroubleshootingDetermining Why USB Support Is Not Present Installing Microsoft USB SupportUpgrade Procedure Multi-Tech Web Site Upgrade OverviewIdentify the MT4X56USB Firmware Identify the Current Firmware VersionClear Your Stored Paramenters Download the Upgrade FileExtract the Upgrade Files Upgrade ProcedureRestore Your Parameters Upgrade the Modem’s FirmwareService, Warranty and Tech Support Software User License Agreement Tech Support Limited WarrantyOn-line Warranty Registration Service, Warranty and Tech SupportContacting Tech Support via E-mail ServiceAppendices Industry Canada Appendix a Regulatory InformationClass B Statement FCC PartAppendices FCC Part 68 TelecomCanadian Limitations Notice FAX Branding StatementInternational Modem Restrictions EMC, Safety and Terminal Directive ComplianceCommission Decision CTR21 New Zealand Telecom Warning NoticeTroubleshooting Appendix B V.90 SupportIntroduction Glossary of Terms MT4X56USB Glossary MT4X56USB Glossary MT4X56USB Glossary MT4X56USB Glossary MT4X56USB Glossary MT4X56USB Glossary MT4X56USB Index IndexConfiguration MT4X56USB Software user license agreement Speed