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Text on Display Description / Cause / Notes
Relays To Terr To Sat Other
P300H P300 Series Installation and Operating Handbook Page 224
Rx Fault: LNB connection/current fault The Modem is configured to feed a DC supply `up the coax` to an LNB, but it detects there is either T
an open or short circuit.
RX WARNINGS (Bottom line of display)
Rx Traffic warnings: Deferred alarm relay only
Rx Warn: Reconfiguring Rx path The modem is reconfiguring the Rx path (after a user parameter change).
Rx Warn: Backward alarm from satellite A Backward Alarm is detected at the Rx Input. This indicates that equipment downstream of the D TB
TRANSMIT path (ie from our modem Tx output, though the Tx chain, through the satellite and then
through the whole distant end Rx path or even further downstream) has failed and is returning an
alarm. This may be due to a receive downstream equipment failure, this Tx chain failing, the satellite
itself, but also possibly the modem Tx output failing. Check the modem Tx path indicates OK,
Check the Tx IF output from the modem is connected to the upconverter equipment and onwards,
monitor the Tx carrier (or distant Rx if possible) with a spectrum analyser.
Rx Warn: CAS MF Back' alm from sat A Multiframe Backward Alarm is detected at the Rx Input, this indicates that equipment downstream D TE
of the TRANSMIT path has failed to find CAS Multiframe sync and is returning an alarm. Note 7
Realistically while this could be caused by any equipment from the Tx modulator onwards, it is
unlikely to be other than the Tx mod, the Rx demod, or further down the Rx path as other failures
would result in a more catastrophic failure (and the correspondingly more significant backward Alarm
above). The Modem only detects this alarm when the Rx baseband is set to use the Insert mux in a
G.732 mode and CAS signalling has been selected (or 2048k IBS G.732 0% overhead mode with
CAS is enabled). Read the text corresponding to “Rx Fault: CAS Multiframe sync lost” to determine
why a CAS multiframe is in use over satellite and Check the three items listed against this message
on the Tx path of this modem.
Rx Warn: Back' alm 1234 from satellite The display may show numbers or dashes (eg “-2-4") corresponding to which of the four backward D
alarms are active at the Rx Input. This indicates that equipment downstream of the TRANSMIT path
(ie the distant end Rx path or further downstream) has failed and is returning an alarm. In
Multidestinational circuits this may NOT correspond to the Tx path of THIS MODEM. The fault may
be due to any receive downstream equipment, but could be due to the relevant modem Tx output
failing. Check the relevant modem Tx path indicates OK, Check the Tx IF output from the modem is
connected to the upconverter equipment and onwards, monitor the Tx carrier (or distant Rx if
possible) with a spectrum analyser.
Rx Warn: O/p clk fail=<source>, now PLL The clock selected as the Receive data output clock, (where <Source> shows the specified clock) D
has failed. The modem has switched to using a backup clock generated by the Rx PLL to preserve
the receive traffic. This fault only occurs if the <source> is the same frequency as the Rx data rate,
otherwise the clock is not used directly instead it is rate converted by the Rx PLL, and it’s failure
results in the fault described immediately below instead. Refer also to the description of the dialogue
under (Change, Rx, Buff/Clk, Rx Clock) to determine which signal the PLL uses as a backup clock.