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SDM-300A Satellite Modem
Fault/Alarm
BUFFER CLK PLL
BUFFER CLK ACT
DEMUX_LOCK
RX 2047 LOCK
BUFFER FULL
RX INSERT
Rev. 4
Possible Problem and Action
Buffer clock phase-locked loop fault. The buffer synthesizer is the
wrong frequency or will not lock.
Ensure the selected buffer clock source is at the proper frequency and
level. If the fault continues, contact the Comtech EFData Customer
Support Department.
Activity detector alarm of the selected interface receive clock.
The interface will fall back to the satellite clock when this fault is
active.
Demultiplexer synchronization lock fault. This fault means that the
demultiplexer is unable to maintain valid frame and multiframe
alignment.
The usual cause is invalid or absent receive data. This is a major
(prompt) alarm. The alarm will cause insertion of receive AIS (all 1s)
and the switch-over will be attempted. This fault is to be sent as a
backward alarm to the distant end. This fault will occur when no carrier
is present, but will probably never occur with a correct signal.
RX 2047 lock alarm.
Indicates the RX 2047 data test pattern is not being received by the
decoder. The alarm probably indicates the transmitter is not set
correctly.
Buffer full alarm.
Indicates the buffer is < 10% or > 90% full.
Insert interface hardware fault (D&I only).
The typical cause of this fault is the insert phase-locked loop is not
locked, or some other insert interface hardware has malfunctioned.
Contact the Comtech EFData Customer Support Department.
Maintenance
5–17
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