Nortel NT1R20 Description page 149

Figure 26
MMI Local loopback test
Meridian 1
Common
Equipment
Figure 27
MMI External loopback test
Meridian 1
Common
Equipment
Line side
T-1
interface
card
Test 2, external loopback, assumes an external loopback is applied to the T1
link. Test data is generated and received by the line-side T1 card on all
timeslots. If test 1 passes but test 2 fails, it indicates that the T1 link is
defective between the line-side T1 card and the external loopback location. If
test 1 was not run and test 2 fails, the T1 link or the line-side T1 card could
be defective. To isolate the failure to the T1 link, tests 1 and 2 must be run in
tandem. Figure 27 demonstrates how an external loopback is applied to the
T1 link.
Line side
T-1
interface
card
NT5D11 Line-side T1 Interface Card
External
T-1 link
network
External
T-1 link
network
Page 125 of 290
Customer
premise
T-1 link
equipment
(CPE)
553-7562
Customer
premise
T-1 link
equipment
(CPE)
553-7563
Line cards Description