HDSL2 System Testing HDSL2 for General Distribution Installation and Maintenance Practice14 61223HDSL2L2-5BFigure 7. Bantam Jack ArrangementsLoopbacksThe ADTRAN HDSL2 modules respond to three different loopback activation processes. Theseprocesses may be utilized to provide a loopback that affects either an H2TU-C or an H2TU-Rmodule (locally or remotely).1. Loopbacks may be activated using the craft interface. The Loopback Options screen thatprovides for the H2TU-C and H2TU-R loopbacks is described in “Control Port Operation”on page 17.2. The modules respond to the industry standard for HDSL loopbacks. A detailed descriptionof these loopback sequences is given in “Appendix A, HDSL2 Loopbacks”.3. HDSL2 modules respond to loopbacks depending on the module type as follows:• H2TU-C modules respond to loopbacks initiated using the software functions describedin 1 and 2 above.• H2TU-R modules respond to loopbacks initiated using front panel pushbuttons. SeeTable 8.ADTRAN HDSL2 modules contain smartloop technology which constantly monitors the DSX-1for a framing pattern. ADTRAN HDSL2 modules will initiate the proper loopback regardless ofhow the loopback control sequence is sent (framed or unframed).The loopback condition imposed in both cases is a logic level loopback at the point within anH2TU-C module where the DSX-1 signal passes into the HDSL2 modulators. Figure 8 depictsall of the loopback locations possible with ADTRAN HDSL2 equipment.DSX-1BRGRxH2TU-CDATAPUMPDSX-1T1R1DSX-1TRHDSL2EQRxDSX-1BRGTxEQTxPOWERTxRxDS1MONCPEDS1INTERFACEH2TURTRT1R1H2TU-C Bantam Jack Arrangement(except DDM+ H2TU-C)H2TU-R Bantam Jack Arrangement
