Nortel Circuit Card 311 Reference page 253

Figure 44
MMI external loopback test
Test 3, network loopback, loops the received T1 data back toward the CPE
equipment. No test data is generated or received by the Lineside T1 card. If
test 2 passes but test 3 fails, it indicates that the CPE device is defective. If
test 2 was not run and test 3 fails, the T1 link or the CPE device could be
defective. To isolate the failure to the CPE device, tests 2 and 3 must be run
in tandem.
how the signaling is looped back toward the CPE equipment.
Figure 45
MMI network loopback test
The Test Carrier (T C) command set enables tests to be run on the Lineside
T1 card, the T1 link, or the CPE device. These three tests provide the
capability to isolate faulty conditions in any one of these three sources.
See
three test types.
After entering the T C command set, select which test to start. The prompt
appears, similar to the following:
Test 1:
Test 2:
Test 3:
(1,2,3 or S to cancel):
Copyright © 2003-2008, Nortel Networks
.
Figure 45 "MMI network loopback test" (page 253)
Table 110 "MMI Tests" (page 254)
Local Loopback Test
External Loopback Test
Network Loopback Test
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Man-Machine T1 maintenance interface software 253
for additional information on these
demonstrates