HDSL4 for General Distribution Installation and Maintenance Practice HDSL4 System Testing61223HDSL4L2-5C 17H4TU-R Front Panel PushbuttonsTwo front-panel pushbuttons, labeled LOC and REM, provide hardware control of theloopbacks.Pressing the LOC pushbutton causes a bidirectional loopback (toward the customer and theH4TU-C) to occur at the H4TU-R. If a bidirectional loopback is active, pressing the pushbuttona second time disables the loopback.Pressing the REM pushbutton activates a bidirectional loopback at the H4TU-C (toward theH4TU-R and network). If the loopback is active, pressing the pushbutton a second timedisables the loopback.Front Panel LED IndicatorsLED indicators mounted on the front panel of the unit provide status of the HDSL4 circuit.Each indicator is described in Table 8 for the H4TU-C and Table 9 for the H4TU-R.Table 8. H4TU-C Front Panel LED IndicatorsModule Label Condition DescriptionDSL 1DSL 2z Greenz RedDSL Loop 1 and Loop 2 sync, no errors currentlydetected, signal margin ≥3 dBNo DSL Loop 1/ Loop 2 sync, errors being detected, orsignal margin < 3 dBDSX/DS1 z Greenz RedDSX-1 signal is present, and no errors currently beingdetectedIn framed mode, denotes loss of framing or loss of sync atthe DSX/DS1 input; in unframed mode, denotes loss ofsignal at DSX/DS1 inputALM { Offz Redz YellowNo active alarm presentLoss of DSX-1 signal to the unitLoss of DS1 signal to the remoteESF/SF { Offz Yellowz GreenUnit is provisioned for unframed dataUnit is provisioned for ESF dataUnit is provisioned for SF dataB8ZS/AMI z Yellowz GreenUnit is provisioned for B8ZS line codeUnit is provisioned for AMI line codeLBK { Offz YellowUnit is not in loopbackUnit is in loopback (network and/or customer)DSL1DSL2TXEQRXTXMONRS232RXDSXDSX/DS1ALMLBKESF/SFB8ZS/AMI
