This test is destructive.

For documentation purposes, the term DS1 applies to the DS1 Interface media modules.

The CSU ELB (Equipment Loopback) test causes a loopback at the near-edge of the local 120A CSU module or T1 sync splitter, and tests the connection from the DS1 board to the CSU module/T1 sync splitter (DS1 board edge interconnecting cable, and CSU module/T1 sync splitter edge). This test will only be performed if the 120A CSU module/T1 sync splitter is present, administered, and connected to a 1.544-Mbps DS1 media module on the back of the port carrier.

The test is destructive and can only be initiated by entering the command test ds1-loop location ds1/csu-loopback-tests.

Enter busyout board to busy out all trunks or ports on the DS1 Interface media module before running the ELB test.

When the ELB test is initiated, maintenance software sends a message to the DS1 Interface media module to start the test. The board sets up the ELB loopback, transmits a test pattern, and verifies that the pattern is received unaltered through the loopback. If the transmitted and received pattern is different, the test fails.

The DS1 media module hardware applies a DC current while the test is running to detect any broken wires that may not be detected by the loopback pattern.

When the test is complete, enter release board to restore all trunks or ports on the DS1 Interface media module to the in-service state.