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NSU-Converter Serial Link
The NSU-Converter Serial Link refers to a dedicated RS485 bus connection between the
NSU and the Backup and Primary converters in the redundancy chain. The NSU-
Converter Serial Link can be enabled or disabled for each chain position independently.
With the NSU-Converter Serial Link enabled for the Backup chain position, when a
Primary Converter fails, its settings are transferred from the NSU to the Backup
converter via the NSU-Converter Serial Link. Once the NSU-Serial Link is enabled for
particular chain positions, the NSU is continuously polling those units updating the
settings stored in the NSU.
Some units in the Redundancy Chain may not be equipped with remote control. An
example would be single band block converters without remote control. In the absence
of an available RS485 connection between the NSU and a particular chain position, the
NSU-Converter Serial Link should be disabled for that chain position.
If the Backup NSU-Serial Link is disabled, a fault in a Primary converter will cause the
transfer switches to switch but none of the settings of the Backup Converter will be
changed. If the Backup NSU-Serial Link is enabled and the NSU-Converter Serial Link
is disabled for a Primary Converter, a fault in that Primary converter will cause the
transfer switches to switch and the Backup converter would be updated with the
converter settings stored in the NSU by the operator.
1.2.5 REDUNDANCY OPERATION
The equipment is capable of being connected in a prioritized redundancy arrangement.
Each redundancy arrangement includes one Backup Unit, and up to twelve Primary
Units. A Switch Module is associated with each Primary Unit. The NSU is capable of
substituting the Backup Unit for any one of the twelve Primary Units on a prioritized
basis.
Redundancy operation is achieved via four-port transfer switches that are located in the
Switch Modules. A Switch Module can be set in one of two states, online or standby.
During normal operation, only one unit in the chain can be in the standby position.
Normally, this would be the Backup Unit. The Primary units would be online. The
Control Unit monitors the Primary Units as well as the Backup Unit via the converter bus.
In the event of a Primary Unit fault: the Control Unit reconfigures the Backup Unit,
switches the Backup Unit online into the primary path, and the faulty Primary Unit to
standby. The faulty unit can then be removed leaving the Switch Module in place
without interrupting signal traffic.
1.2.5.1 REDUNDANCY MODES
There are two redundancy modes available, manual and automatic.