ADTRAN DSU 5600 User Manual

61200.078L1-1 DSU 5600 User Manual 2 3Chapter 3. Test ModesREMOTE TESTSThe DSU 5600 responds to three remote activated tests:• Remote Digital Loopback (RDL)• CSU Loopback (LL)• DSU Loopback (RT)The RDL test is initiated by a remote DSU and causes the localDSU 5600 to loopback. The loopback point is the same as theLoop Only point shown in Figure 3-4. This test is run to test theend-to-end performance of the circuit.Both the CSU Loopback and the DSU Loopback tests are acti-vated from the telephone company diagnostic test equipmentand are used to isolate trouble on a circuit.The CSU Loopback, commonly called the LL test, has the sameloopback points as the DTE and Loop test. It is used by thetelephone company to test the integrity of the local loop.The DSU Loopback, commonly called the RT test, has the sameloopback point as the Loop Only test and is used by the tele-phone company to test the operation of both the local loop andDTE interface sections.