ETC CEM3 v1.5.1 - Manual (Page 59)

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Redundant Tracking Systems 53
The switchover from A to B for dimming happens instantaneously, so that control of lights
is not lost. However, the switchover of the user interface has built in hysteresis to eliminate
bounce in certain circumstances (for example, when DMX is lost, both processors may not
see and account for the DMX loss at exactly the same time). For this reason it may
sometimes appear to take a long time for the user interface of the backup unit to start up;
however, bear in mind that dimming control always transfers near-instantaneously,
however some hysteresis is required for the startup of the user interface.
Configuration Management in Redundant Tracking Systems
In a tracking CEM3 system the two processors automatically communicate and
synchronize their configurations though the backplane - no external Ethernet network is
needed for the two processors to synchronize data.
Once you make a configuration change on one processor, that change is automatically
transferred to the second processor.
When the system boots up, it is assumed that the A processor has the most recent
configuration, so the configuration will be automatically transferred from A to B if B has a
different configuration.
Firmware Upgrades in Redundant Tracking Systems
When you upgrade firmware in a redundant system (either via the network or using a USB
key), the firmware upgrade is automatically transferred to both processors. Once the
firmware is transferred the upgrade will occur on both processors simultaneously.
Therefore it is not necessary to update both processors independently in a rack.
Rack 1 - CEM3 Rack
System OK
DMXA: 1 DMXB: Off
sACN: 2/1
[Info]
CEM3 Control
Backup Active Processor A
Processor B