Comtech EF Data XTRT-400C Operation And Installation Manual page 190

External Reference Detection and Lock Fault Configuration:
There are three faults related to the external reference. The
behavior of these faults is configurable via specific factory
configuration serial commands. It is best to specify the desired
behavior at the time of order, but the configuration may be adjusted
in the field by factory trained personnel. Factory Default
configurations are listed below in Table 1.
The three fault lines related to the external reference are:
Ext Ref Present - This feature is available only if the HPA includes
an internal Phase Locked Oscillator (PLO), that is intended to
improve the phase noise, and/or shift the frequency of an optional
customer supplied reference (see Figure 5). This fault line senses
the presence of the required reference frequency at approximately
the proper power level. HPA function is disabled if the reference
frequency is not detected when this feature is enabled. This feature
can be disabled (turned off) if desired. If this feature is disabled,
and the external reference is not supplied, the internal PLO will
"free-run" and generate the necessary reference frequency for HPA
operation. See the factory default setting below.
Ext Ref Lock - This feature is availalbe if the HPA includes an
internal Phase Locked Oscillator (PLO), that is intended to improve
the phase noise, and/or shift the frequency of a customer supplied
reference (See Figure 5). This fault line indicates the proper
function of the phase locked loop, (PLL), in either the PLO or the
standalone reference. This feature can be disabled (turned off) if
desired. If this feature is disabled, and the external reference is not
supplied, the internal PLO will "free-run" and generate the
necessary reference frequency. See the factory default setting
below.
Upconverter fault Configuration (latching vs non-latching):
All HPAs that include block frequency upconverters will disable
operation, and an upconverter fault will report, if the lock detect
senses the absence of required reference frequency or a loss of
lock in the PLL. The upconverter fault is configured by a default to
be a latching fault, which requires a fault reset to clear, once the
fault condition has been corrected.
Alternatively, the HPA may be configured to automatically clear an
MNC-0000-015
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Operation Addendum, Block Upconverter
9 of 10 Revision F