Comtech EF Data DMD2401/DMD2401L - Manual (Page 177)

Maintenance DMD2401/DMD2401L/DMD2401 IBS/IDR Satellite Modem
6-2 TM065 – Rev. 3.3
6.2.1 Alarm Masks
The user has the capability to ‘Mask’ individual alarms on the DMD2401. When an Alarm is
masked, the front panel LEDs and the Fault Relays do not get asserted, but the Alarm will still be
displayed. This feature is very helpful during debugging or to lock out a failure that the user is
already aware of.
6.2.2 Active Alarms
6.2.2.1 Major Alarms
Major alarms indicate a modem hardware failure. Major alarms may flash briefly during modem
configuration changes and during power-up but should not stay illuminated. Alarms are grouped
into Transmit alarms and Receive alarms - Transmit and Receive are completely independent.
6.2.2.2 Minor Alarms
Minor alarms indicate that a problem may persist outside the modem such as loss of terrestrial
clock, loss of terrestrial data activity, or a detected transmit or receive AIS condition.
Alarms are grouped into Transmit Alarms and Receive Alarms - Transmit and Receive are
completely independent.
6.2.2.3 Latched Alarms
Latched alarms are used to catch intermittent failures. If a fault occurs, the fault indication will be
latched even if the alarm goes away. After the modem is configured and running, it is
recommended that the latched alarms be cleared as a final step.
6.3 DMD2401 Fault Tree Matrices
Tables 6-1 through 6-3 represent, in matrix form, the faults that may occur within the DMD2401.
There are three matrices: Interface/Common Equipment Faults, Tx Faults and Rx Faults.
Table 6-1. DMD2401 Interface/Common Equipment Fault Matrix