Nortel Networks 553-3001-211 manual NT5D33 and NT5D34 Lineside E1 Interface cards Page 297

NT5D33 and NT5D34 Lineside E1 Interface cards Page 297 of 894

Figure 57

MMI External loopback test

	System
Common	Line side		External		Customer
	E-1	E-1 link		E-1 link	premise
Equipment	interface		network		equipment
	card				(CPE)
					553-1161

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 58 illustrates how the signaling is looped back toward the CPE.

Figure 58

MMI Network loopback test

	System
Common	Line side		External		Customer
	E-1	E-1 link		E-1 link	premise
Equipment	interface		network		equipment
	card				(CPE)
					553-1162

Circuit Card Description and Installation