Alarm Masks; Active Alarms; Major Alarms; Minor Alarms - Comtech EF Data DMD50 Installation And Operation Manual

DMD50 Univeral Satellite Modem
+20V SUPPLY
EXT CLOCK ACT
EXT REF ACT
EXT REF LOCK

6.2.2 Alarm Masks

The modem performs a high degree of self-monitoring and fault isolation. The alarms for these
faults are separated into the following three categories:


Active Alarms


Common Equipment Alarms

Backward Alarms
A feature exists that allows the user to 'Mask' out certain alarms as explained below.
Masking alarms may cause undesirable modem performance.
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 of which the user is already aware.
6.2.2.1 Active Alarms
6.2.2.1.1

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 and Receive Alarms - Transmit and Receive are completely independent.
6.2.2.1.2

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 and Receive Alarms - Transmit and Receive are completely
independent.
MN-DMD50– Revision 3
Displays the measured voltage of the +20 Volt power bus located inside the
modem.
Indicates that the External Clock is not active.
Indicates no activity on the External Reference.
Indicates that the External Reference PLL is not locked.
Maintenance and Troubleshooting
6–5