13Section 61104020L4-5, Issue 361104020L4-5CDuring a remote end initiated loopback the systemtransmits ASC 9Eh toward the network, indicating anout-of-service condition generated by the remote end,as shown in Figures 10 and 11.All IDSL/DDS system latching loopbacks, whetherinitiated by the IDSL DCU-R craft interface, LBKpushbutton, CO, or from a remote Test Center, can bereleased by sending 35 DDS loop down TIP bytes (Where X is a “don’t care” bit). Allexisting latching loopbacks will also be disabled bypressing the LBK pushbutton on the CO or remoteunit.NOTEThe remote end test feature is only supportedwhen the upstream U-BR1TE is an ADTRAND4 or Series 5 U-BR1TE with DDS Loopbackcapability. Other U-BR1TEs will ignore theloopback command sent by pressing the IDSLOCU-R LBK button.IDSL/DDS Trouble CodeThe IDSL/DDS system provides a quick diagnosis inthe case of a circuit condition where continuity isbroken. The trouble code type received by a testerdetermines whether the open condition is occurring onthe local loop or at the customer premises. In theevent of a 2-wire DSL loss of signal, loss of sync, oropen condition caused by an open conductor ordisconnected 2-wire loop, the U-BR1TE V transmits aMUX-Out-of-Sync trouble code (MOS 9Ah) into thenetwork as shown in Figure 12. During a similarout-of-service condition at the customer premises, theIDSL OCU-R transmits Abnormal Station Code(ASC 9Eh) upstream toward the network as shown inFigure 12.2B Leased Mode OperationThe U-BR1TE V is deployed in 2B leased lineoperation to provide DDS/Frame Relay services toISDN equipment. By using the 2-wire ISDN interfacefor 128 kbps data rate, the U-BR1TE V Leased ModeOperation allows pair savings over traditional DDSdeployment. DDS/Frame Relay support allowsloopback testing to be performed across the ISDNtransport system in this configuration.The U-BR1TE V will decode DDS latching loopbacksequences coming from the carrier into eoc loopbackcommands usable by traditional ISDN equipment. SeeFigure 13 for various U-BR1TE V DDS 2B LeasedMode arrangements. In a SLC-96 network theU-BR1TE V units will operate in both 2B+D or 2Bmode. Both units must be in the same mode.Loopback OperationTo enable detection of DDS latching loopbacks, theADTRAN U-BR1TE V must be provisioned as anLT- like device in leased 128 kbps (2B) mode ofoperation.When B1 and B2 are enabled, data on both channelsare looped in response to a DDS latching loopbacksequence detected on channel B1. The U-BR1TE Vwill respond to a DS0 latching loopback intended forDS0 #1. Loopback commands intended for DS0 #2and greater are re-mapped to ISDN eoc loopbackcommands addressed to the appropriate unit.The U-BR1TE V will map a CSU latching loopbacksequence to an ISDN eoc NT1 loopback. Figure 13shows the DDS latching loopback commands that willloop each unit.NOTEOnly the B1 channel will detect the DDSloopback sequences for activation anddeactivation of DS0 and CSU latchingloopbacks. All standard U-BR1TE units betweenthe ADTRAN U-BR1TE V and the NT1 devicemust have the D-channel enabled in order forloopbacks to be processed beyond theU-BR1TE V.Figure 12. IDSL/DDS Trouble CodesMOS 9AhChannel BankOpen 2-wire LoopDSUIDSL OCU-RCustomer PremisesASC 9EhChannel BankASC 9EhOpen 4-Wire CustomerInterfaceDSUIDSL OCU-RCustomer PremisesU-BR1TEIVU-BR1TEIV
