3Com 5108M-TP manual Channel Select Switch Settings

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The Off position sets the Squelch level to low. When the Squelch level is set to low, the ports are able to receive weaker signals. Note that Low Squelch mode does not conform to the 10BASE-T standard. If you change the module's Squelch level to low, you must change the 10BASE-T Transceiver Squelch level to low also. Refer to the ONline Ethernet 10BASE-T Transceiver Installation Guide for information on setting the transceiver Squelch level.

On unshielded twisted pair cable, setting the Squelch level to low increases the achievable link distance by approximately 25% to 50%, but with the added risk of losing packets to impulse noise. Do not use Low Squelch mode if your network should experience too many illegally short packets (runts). This problem will occur if there is significant external noise around the link.

Setting the Squelch level to low in conjunction with shielded twisted pair wiring increases the achievable link distance without sacrificing noise immunity. Thus, there is no realdrawback in using Low Squelch on shielded twisted pair.

To gain the extended link distance achieved by using Low Squelch mode, you must use qualified data grade shielded twisted pair cable or qualified high performance unshielded cable. IBM Type 1 shielded cable (with an appropriate RJ45 to Type 1 connector), among others, meets this requirement. If you are unsure of the grade of twisted pair cable to use, set the Squelch level to high, or call 3Com for a list of qualified cables to use in extended distance applications.

Channel Select Switch Settings

The ONline Ethernet 10BASE-T Module is equipped with the technology to work with the ONline System Concentrator's unique TriChannel™ architecture. This feature allows you to assign the module to any of three channels (or none) on the ONline System Concentrator backplane. Refer to Chapter 1 in the ONline System Concentrator Installation and Operation Guide for a complete discussion of ONline's TriChannel architecture.

The channel select switch settings (switches 2 and 3) on dip switch SW3 let you select a channel. Switches 2 and 3 are factory set to On, therefore, the

1 - 8 ONline Ethernet 10BASE-T Module User’s Guide

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Contents ONline Ethernet 10BASE-T Module User’s Guide Ii ONline Ethernet 10BASE-T Module User’s Guide ONline Ethernet 10BASE-T Module User’s Guide Iv ONline Ethernet 10BASE-T Module User’s Guide Contents Installing and Operating the Module Figures Viii ONline Ethernet 10BASE-T Module User’s Guide Tables Page How to Use This Guide AudienceStructure of This Guide Document Conventions Convention Indicates ExampleUsr/snm/agents Related Documents 3Com Documents Reference DocumentsPage Introduction ONline Ethernet 10BASE-T ModuleIndicators BASE-T Module Faceplate and ONline System Concentrator Dip Switches Interpretation of the 10BASE-T Module LEDsLED Name Color State Indicates Dip Switch SW1 Port Status Dip Switch SW3 Crossover Mode, Channel Select, Squelch Dip Switch SW1 Settings and InterpretationsDip Switch SW3 Settings for Switches 1 Switch Function Factory Switch Setting Default OffCrossover Mode Switch Squelch Mode SwitchChannel Select Switch Settings Dip Switch SW3 Settings and Interpretations for Switches 2 Switch Channel SelectionRelated Features Dip Switch SW6 Settings and InterpretationsEnable LED State Channel Configuration Channel Check CodesPage Designing and ExpandingtheNetwork Understanding the General Rules Basic Network RulesSeven Basic Network Rules Rule Definition Recommendations/NotesCertain LAN devices Seven Basic Network Rules LAN Equivalence LAN Product Equivalent DistancesLAN Product Equivalent Distance meters Fiber Backbone, Twisted Pair To-The-Desk Fiber Backbone, Twisted Pair To-The-Desk Example Sample Configuration Distance Calculation Maximum Link Distance on Twisted Pair Unshielded Twisted Pair High Squelch Low SquelchShielded Twisted Pair High Squelch Low Squelch IBM Type Twisted Pair Backbone, Twisted Pair To-The-Desk Unshielded Twisted Pair NetworkRedundant Twisted Pair Configuration Redundant LinksPage Patch Panels Installing and Operating the Module Precautionary ProceduresUnpacking Procedures Installation ProceduresInstalling a 10BASE-T Module BASE-T Module Cable Connection Troubleshooting TroubleshootingTroubleshooting With the Status LEDs Troubleshooting With the Port Status LEDsTroubleshooting With the Port Status LEDs Troubleshooting With the Port Status LEDs Troubleshooting With the Activity LEDs Troubleshooting With the Port Activity LEDsPossible Problem Troubleshooting State Solutions LED NameTechnical Assistance ONline Ethernet 10BASE-T Module Specifications Electrical SpecificationsEnvironmental Specifications Mechanical SpecificationsGeneral Specifications Twisted Pair Connectors and Cables Twisted Pair ConnectorsFigure A-1. RJ45 Connector Pin-outs Twisted Pair CablesConnecting Twisted Pair Cables Page Technical Support On-line Technical SupportSupport from Your Network Supplier Email Technical SupportWorld Wide Web Site Support from 3Com Accessing the 3Com MIB Returning Products for Repair3Com Technical Publications Page Index MIB, B-4