Nortel Circuit Card Installation Manual page 309

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