User manual

Wide Bank 28 DS3 - Release 2.4 July 2004 7-37

Diagnostics & Troubleshooting

Testing DS3 Interfaces

Testing the DS3 Far-End with Loopback Tests

When the Wide Bank is configured for C-bit framing, the following DS3 far-end loopup and

loopdown control is available.

The command that controls the far-end DS3 loop mode sends either a loop up code or a loop down

code:

ds3 send [loopup|loopdown]

When a DS3 Activate Loopback command is received, the DS3 is set to a LINE loopback mode.

The loopback status can be observed by the ds3 and status ds3 commands. Also, the Controller

Status LED is set to YELLOW.

Far-End Loop Codes

When a far-end loop command is issued at the near-end, the selected Line Loopback Activate

or Deactivate code word is transmitted ten times to the far-end, followed immediately by the

selected low-speed or DS3 Line code word (also transmitted 10 times). See Table 2-1. The total

message to the far-end is 40 octets long (each code word is two octets).

NOTE: The labels for the loopback code words are determined by ANSI T1.107, so the

following chart refers to DS1 exclusively. However, the same loopback functions and code

words apply to E1 as well, with the exception that every fourth low-speed circuit is not used

with E1.

The DS1 code words use bits 3 - 7 to indicate which line is to be looped back.

Table 2-1 Far-End Loopback Code Words

Loopback Function Loopback Code Word

Activate Line Loopback 00001110 11111111

Deactivate Line Loopback 00111000 11111111

Select DS3 Line 00110110 11111111

Select DS1 Line 1 01000010 11111111

Select DS1 Line 2 01000100 11111111

Select DS1 Line 3 01000110 11111111

Select DS1 Line 4 (not E1) 01001000 11111111

Select DS1 Line 5 01001010 11111111

Select DS1 Line 6 01001100 11111111