Nortel Networks Circuit Card - Manual (Page 309)

NT5D33 and NT5D34 Lineside E1 Interface cards Page 309 of 906
Circuit Card Description and Installation
Figure 60
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. Figure 61
illustrates how the signaling is looped back toward the CPE.
Figure 61
MMI Network loopback test
E-1 link
Line side
E-1
interface
card
Customer
premise
equipment
(CPE)
Common
Equipment
System
External
network
E-1 link
553-1161
E-1 link
Line side
E-1
interface
card
Customer
premise
equipment
(CPE)
Common
Equipment
System
External
network
E-1 link
553-1162