Chapter 3. Test Modes
61200062L1-1 DSU 56/64 User Manual 3-9
REMOTE TESTS
The DSU 56/64 responds to three remotely activated tests.
• Remote Digital Loopback (RDL)
•CSU Loopback (LL)
• DSU Loopback (RT)
The RDL test is initiated by a remote DSU and causes the local DSU
56/64 to loopback. The loopback point is the same as the loop only
point. See Figure 3-4 on page 3-6. This test is run to test the end-to-
end performance of the circuit.
Both the CSU LOOPBACK and the DSU LOOPBACK tests are
activated from the telephone company diagnostic test equipment
and are used to isolate trouble on a circuit.
The CSU LOOPBACK, commonly called the LL test, has the same
loopback points as the DTE AND LOOP test. It is used by the
telephone company to test the integrity of the local loop.
The DSU LOOPBACK, commonly called the RT test, has the same
loopback point as the LOOP ONLY test and is used by the telephone
company to test the operation of both the local loop and DTE
interface sections.