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System-level Troubleshooting 363
Digital Line Card
Troubleshooting
In order to correctly troubleshoot a Digital Line Card, you must determine
whether the origin of the problem is:
■ The hardware
■ The software configuration
■ The CSU (Channel Service Unit)
■ The telephone company’s line
To eliminate the Digital Line Card (T1 or E1) attach a loop back connector
in place of the telephone company’s line. Configure the card as described
in the appropriate section of Chapter 3
.
After you complete the configuration, and with the loopback connector
in place, verify that the Nominal status light on the front panel of the T1
or E1 Digital Line Card is turned on (appears steady and green).
■ If the Nominal status light does not turn on, the problem is most likely
in the Digital Line Card, and you should contact your 3Com
Voice-Authorized Partner to report the problem.
■ If the Nominal light turns on, the problem is either in the CSU
(Channel Service Unit) or in the telephone company’s line. Contact the
telephone company for assistance.
Alarm Conditions
(Overview)
T1 and E1 Digital Line Cards may experience these alarm conditions:
■ Red Alarm — Indicates one of these conditions:
■ Loss of Signal (LOS)
■ Loss of Framing (LOF) also known as Out of Frame (OOF)
■ Blue Alarm — Indicates an Alarm Indication Signal (AIS)
■ Yellow Alarm — Indicates a Remote Alarm Indication (RAI)
An alarm condition may be a:
■ Signal — Information transmitted either in the upstream or
downstream direction, warning of a detected failure:
■ State — A condition, activated at a terminal device, indicating that a
problem exists and remedial action is required.
T1 and E1 Digital Line Cards are considered “downstream” equipment.