434 CHAPTER 18: T ROUBLESHOOTINGby the Central Office or by test equipment emulating Central Officeequipment. For more information about how to enable loopback tests,see “Using Loopback Tests” on page 188.After you complete the configuration, and with the loopback connectorin place, verify that the Nominal status light (3C10165C E1 card or3C10116C T1 card) on the front panel of the Digital Line Card is turnedon (appears steady and green). For the 3C10165D E1 card and3C10116D T1 card, make sure the CO status light is green.■ If the Nominal or CO status light does not turn on, the problem ismost likely in the Digital Line Card. Contact your 3ComVoice-Authorized Partner to report the problem.■ If the Nominal or CO light turns on, the problem is either in the CSU(Channel Service Unit) or in the telephone company’s line. Contact thetelephone company for assistance.The 3C10165D E1 Card and the 3C10116D T1 card each have anonboard CSU. You can view CSU statistics for the card through the NBXNetSet utility. For more information see “Viewing CSU State Informationand Statistics” on page 185.Alarm Conditions(Overview)T1 and E1 Digital Line Cards might 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 might be one of these:■ Signal — Information transmitted either in the upstream ordownstream direction, warning of a detected failure:■ State — A condition, activated at a terminal device, indicating that aproblem exists and remedial action is required.T1 and E1 Digital Line Cards are considered “downstream” equipment.
