Nortel Meridian 1 Option 11C Manual page 96

Page 96 of 126 PRI Maintenance
553-3011-315 Standard 13.00
Yellow (Far End) Alarms
A Yellow alarm on the 2.0 Mb PRI card indicates that the card is receiving an
alarm indication from the far end.
This type of alarm may be received in two ways:
• Remote Alarm Indication (RAI)—Bit 3 of non-FAS frame set
• Alarm Indication Signal (AIS)—All 1s on the carrier.
Since the 2.0 Mb PRI is receiving a Yellow alarm signal, that indicates that
there is a carrier connection, but the far end is not ready. It is possible,
however, that the carrier connection is one way only (2.0 Mb PRI receiving).
When the 2.0 Mb PRI receives a Yellow alarm signal, all channels are placed
in a maintenance busy mode (MBSY). Group 2 Yellow alarms are recorded
(LCNT) on each occurrence, but the card is not placed into an out-of-service
state.
Red (Local) Alarms
A Red alarm on the PRI card indicates that the card is having problems
synchronizing with the incoming bit stream.
This type of alarm may be caused by the following:
• Loss of Signal (LOS)
• Loss of Frame Alignment (LFAS)
• Loss of CRC-4 Multiframe Alignment (LMAS)
When the 2.0 Mb PRI is in a Red alarm state, RAI is transmitted to the far end.
For both Group 2 Red and Yellow alarm states, action is taken after the
condition has persisted for a downloaded persistence (PERS) threshold. The
parameter is set in LD 73 in multiples of 2 msec, with 2 x 50 = 100 msec as
the default.
For Group 2 Red alarm conditions, there are four definable time thresholds
that can be set in LD 73 on a per-loop basis. The first parameter sets an
aggregate time in multiples of 128 msec (default 20=2.5 sec). The next four
parameters provide time thresholds for MAINT, NNDC, NNC, and OOS.
January 2002
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