ADC HDSL4, H4TU-C-319 List 1 Line Unit user manual Loopback Operation, Loopback Summary

Testing LTPH-UM-1031-03, Issue 3

LOOPBACK OPERATION

HDSL4 has a family of loopback options for analyzing circuit functionality. The loopback signal is transmitted and returned to the sending device for comparison. This allows you to verify the integrity of the HDSL4 channels to the H4TU-C, the H4TU-C DSX-1 interface, and the DS1 channels to the customer.

Loopback options include:

•Generic Loopback (GNLB) options, including the SmartJack (SMJK) option (see Table 16 on page 51)

•A3LB Addressable Repeater Loopback command (see Table 17 on page 52)

•A5LB Addressable Repeater Loopback command (see Table 18 on page 53)

Loopback commands can be initiated by:

•Selecting the loopback type using the MODE and SEL pushbuttons on the H4TU-C front panel or the manual loopback (LBK) pushbutton on the H4TU-R front panel

•Selecting the loopback type from the Monitor menu when connected to the craft port of the H4TU-C or H4TU-R

•Entering the loopback code (exceptions are COLB and RULB) into the test equipment connected to the H4TU-C or H4TU-R

Activate loopback using one of the following:

•MODE/SEL pushbuttons

•Maintenance Terminal

•Test Set

	Span 1
DSX-1
NLOC	CREM	NDU1
	H4TU-C	H4D1

Span 2

CDU1 NDU2

Span 3

NREM

CDU2 SMJK

TLOS*

H4D2

CLOC

H4TU-R

Activate loopback using one of the following:

•LBK pushbutton

•Maintenance Terminal

•Test Set

* When enabled, TLOS is an automatic loopback that occurs with an LOS at the remote DS1 input.

Network	Customer
	Premises

Figure 28. Loopback Summary

ADC HDSL4 supports multiple loopbacks, but a single loopback is the preferred method. HDSL4 automatically rejects activation of closed loop looopbacks. For example, an NREM and CREM cannot be activated at the same time.

46 September 12, 2003 H4TU-C-319 List 1