Alcatel-Lucent 9500 MXC User Manual page 189

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Where both RACs are in receive path alarm because of a path problem, no signal is received in either
direction. In such situations the 'silent Tx' switch command will be prompted by receive path alarms at
both ends of the link, but will not be received at the transmit ends of the link.
3DB 23063 ADAA - Rev 004 July 2007
• Transmitter path failure, Hot-standby and Space Diversity:
• Tx synthesizer not locked
• Tx transceiver failure
• Tx power failure
• Tx ODU IF synthesizer not locked
• Tx RAC IF synthesizer not locked
• Modulator not locked
• ODU cable unplugged
Transmitter switching is also remote-end initiated in the event of an undetected
'silent transmitter' failure.
• This occurs when both online receive RACs are in receive alarm, whereupon a
switching command is returned to the local-end transmitter
• This remote-initiated switch is designed to prevent a silent transmit failure
(failure cannot be detected by the local hardware/software) from causing the
link to go down indefinitely.
A silent Tx switch is initiated when both the demodulators have lost lock or both
receivers have lost frame synchronization (demodulator not locked alarm).
Transmit Switching Criteria, Frequency Diversity:
Both transmitters are operational. A switch only affects the online status of the
RACs, which for frequency diversity is the RAC controlling transmit
synchronization.
Online RAC Tx switching is initiated for the following conditions:
• RAC plug-in is missing or incorrect
• RAC software load failure
Manual return to primary RAC transmit requires a 9500 MXC CT command in the
System/Controls screen. This should be forced for hot-standby installations using
an unequal coupler where the primary RAC is assigned to the low-loss side.
9500 MXC User Manual
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Vol. II-3-95