Nortel Circuit Card 311 Reference page 313

Figure 78
MMI Local loopback test
Test 2, external loopback, applies an external loopback to the E1 link. Test
data is generated and received by the LEI on all timeslots. If test 1 passes
but test 2 fails, it indicates that the E1 link is defective between the LEI and
the external loopback location. If test 1 was not run and test 2 fails, the E1
link or the LEI could be defective. To isolate the failure to the E1 link, tests 1
and 2 must be run in tandem.
313)
Figure 79
MMI External loopback test
Test 3, network loopback, loops the LEI's received E1 data back toward the
CPE. No test data is generated or received by the LEI. 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 E1 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.
80 "MMI Network loopback test" (page 314)
looped back toward the CPE.
Copyright © 2003-2008, Nortel Networks
.
Man-Machine E1 maintenance interface software 313
demonstrates how an external loopback is applied to the E1 link.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Figure 79 "MMI External loopback test" (page
illustrates how the signaling is
Figure