Appendix A. 1:1 REDUNDANCY
A.1 Introduction to Redundancy Operation
The LPOD can be used in a redundancy configuration by connecting the appropriate 1:1
redundancy cable to the J6 COM1 Connector (see Chapter 2. SYSTEM CONNECTIONS,
INSTALLATION
AND OPERATION). Once the cable is attached, with the units placed in
redundancy mode via the correct remote command, the system automatically configures the
backup (offline) unit by copying the configuration from the active (online) unit.
A.2 1:2 Redundancy Mode
1:2 Redundancy Mode is supported via an external controller box and is not discussed in this
appendix.
A.3 1:1 Redundancy Mode
In 1:1 redundancy mode, the unit that is currently not the active (online) unit (as determined by
the switch position) will be the controlling backup (offline) unit.
The serial command
ESW determines system operation. If ESW=1 (TX Only) or ESW=2 (TX +
RX) is executed in both units, the system will be in Automatic Redundancy mode. In this mode, if
a fault is detected with the active (online) unit – either by loss of communications between the
backup (offline) and active units, or via the summary fault – the backup unit will trigger the
waveguide switch and, assuming the backup unit is not faulted, will become the active unit. The
backup unit will also poll the active unit at regular intervals in an attempt to maintain
configuration compatibility with the active unit; this ensures that, should a fault occur, the backup
unit is configured exactly the same as the active unit.
The LPOD redundant mode does not specify which unit must be the backup (offline) unit.
Instead, the status of the backup (offline) and active (online) units are determined by the
waveguide switch position. The advantage to using this redundant method is that, after a failure is
detected and the backup unit causes a redundant switchover to occur, the failed unit can be
replaced without forcing a second switchover to occur. This is because the backup unit becomes
the active unit, and when another unit is installed in the system it automatically becomes the new
backup unit.
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