Loopback Operation

152-402-145-02, Issue 2

 

 

LOOPBACK OPERATION

HiGain HDSL2 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 HDSL2 channels to the H2TU-C, the H2TU-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 10 on page 25)

•Special Loopback (SPLB) options (see “Special Loopback Commands” on page 26) and the following command tables:

–Addressable Repeater Loopback command: A2LB (see Table 11 on page 28)

–Addressable Repeater Loopback commands: A3LB, A4LB (see Table 12 on page 30)

Loopbacks can be initiated by:

•Selecting the loopback type using the MODE and SEL buttons on the H2TU-C front panel

•Selecting the NREM-CLOC dual loopback using the LBK button on the H2TU-R front panel

•Selecting the loopback type from the Monitor screen when connected to the H2TU-C or H2TU-R craft port

•Entering the loopback code into the test set connected to the craft port of the H2TU-C or H2TU-R

The H2TU-R-402 List 4E performs a metallic loopback self test when looping up an NREM or SMJK loopback.

HiGain HDSL2 supports multiple loopbacks, but a single loopback is the preferred method.

Generic Loopback Commands

The HiGain HDSL2 Generic Loopback (GNLB) commands allow you to use inband codes to loop up either NLOC (4-in-7) or NREM (3-in-7) towards the network. In addition, these inband codes loop up CREM (6-in-7) or CLOC (5-in-7) towards the customer. Either loopup condition can be terminated (looped down) with the 3-in-5, SMJK loopdown code. All inband codes must be present for at least 5 seconds before the HiGain HDSL2 system responds. TLOS is a logic loopback caused by loss of the DS1 input from the CI.

Figure 21 summarizes the available loopbacks in the system, and Table 10 on page 25 summarizes the HiGain HDSL2 generic loopback commands. See “GNLB Test Procedures” on page 26 for the test procedures that apply when using the GNLB mode.

Activate loopback using

 

 

 

 

 

 

 

 

 

 

 

 

 

Activate loopback using

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

one of the following:

 

 

 

 

 

 

 

 

 

 

 

 

 

one of the following:

• MODE/SEL pushbuttons

 

 

 

 

 

 

 

NREM

 

 

 

 

 

• LBK pushbutton

• Maintenance Terminal

 

 

 

 

 

 

 

 

 

 

 

 

• Maintenance Terminal

 

NLOC

 

 

CREM

SMJK

 

 

CLOC

• Test Set

 

 

 

 

 

• Test Set

 

 

 

 

 

 

 

TLOS

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

H2TU-C

 

H2TU-R

 

 

 

 

 

 

 

Network

Customer

Premises

 

Figure 21. Loopback Summary

24

June 16, 2000

H2TU-R-402