GE Mark VIe Instruction Manual page 9

Data outputs from dual redundant controllers are normally implemented with each controller sending its signal to its switch
and each switch forwarding the signal to one of the two ports on an I/O pack on an I/O module. The pack uses the first
healthy reference that it sees and continues to use it until it is not available or the pack determines that the signal is unhealthy.
This results in a transfer to the second reference with no latency in driving outputs. In the unlikely event that an output pack
loses communication with both IONETs, it defaults to one of three pre-configured states: 0 = Power Down State,
1 = Preset Value State, 2 = Last Value State.
Instruction Guide GEI-100728A 9
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