ADTRAN DSU 56/64, User Manual

Page: 37 / 44

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 L
OOPBACK
and the DSU L
OOPBACK
tests are
activated from the telephone company diagnostic test equipment
and are used to isolate trouble on a circuit.
The CSU L
OOPBACK
, commonly called the LL test, has the same
loopback points as the DTE
AND
L
OOP
test. It is used by the
telephone company to test the integrity of the local loop.
The DSU L
OOPBACK
, commonly called the RT test, has the same
loopback point as the L
OOP
O
NLY
test and is used by the telephone
company to test the operation of both the local loop and DTE
interface sections.