Loopback Operation

152-402-145-02, Issue 2

 

 

Special Loopback Commands

In addition to the GNLB loopback command mode, a HiGain HDSL2 system can be configured for one of three special loopback command modes. These command modes, A2LB, A3LB, and A4LB, are selected from the ADC Options maintenance terminal screen or by using the MODE and SEL buttons on the H2TU-C front panel. Once a loopback mode is activated, other loopback commands can be sent by a test set connected to the craft port on the H2TU-C or H2TU-R front panel.

A2LB through A4LB are special, addressable, repeater loopback modes that are supported by the H2TU-R-402 (see Table 11 on page 28 and Table 12 on page 30 for list of Addressable Repeater Loopback Commands). These loopback modes provide the HiGain HDSL2 system with sophisticated maintenance and troubleshooting tools.

A2LB is patterned after the Teltrend addressable T1 repeater loopbacks. A3LB and A4LB are patterned after the Wescom addressable T1 repeater loopbacks.

These addressable repeater loopback modes have been enhanced to handle the specific requirements of the following HiGain HDSL2 customers:

•A2LB (Teltrend) = Southwestern Bell

•A3LB (Wescom) = New England Telephone, Bell Atlantic

•A4LB (Wescom Mod 1) = New York Telephone

A2LB can be configured to do one of the following:

•Block the arming code (after 2 seconds) from exiting the H2TU-C into the network, and replace it with the AIS code.

•Unblock the AIS code by executing the Far End Activate code.

A3LB differs from A4LB in that A3LB supports the additional (1-in-6) SMJK loopback command.

SMJK loopback commands are only activated by inband commands.

LOOPBACK TEST PROCEDURES

The following sections provide step-by-step test procedures for verifying the integrity of the HDSL2 channels at every module location as well as the DS1 channels to the customer and the local DSX-1 interface.

GNLB Test Procedures

Figure 22 on page 27 is a graphical representation of the various loopback configurations with the associated GNLB commands shown. Also, refer to Table 10 on page 25 for a description of these commands.

To perform the GNLB loopback test procedure:

1Have the CO tester send the NREM (3-in-7) inband loopup code for 5 seconds. The LBK LED on the front panel should be a steady yellow, and the loopback mode should be identified on the Monitor screen.

2Have the CO tester transmit a DS1 test signal towards the H2TU-R-402 and verify that the returned (looped) signal to the test set is error-free.

3If step 2 fails, have the CO tester transmit the 3-in-5 inband loopdown code.

4Have the CO tester send the NLOC (4-in-7) inband loopup for 5 seconds. You should be able to observe the NLOC message on the Monitor screen.

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June 16, 2000

H2TU-R-402