From the AMM, I never create nothing, but I know how to use it !!!
ISIS Indicator
The ISIS indicator is supplied with 28VDC from:
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the ESS BUS (403PP) first, (when the aircraft electrical network is energized)
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and the HOT BUS (701PP), when the speed detected by the ADIRUs 1 and/or 3 is more than 50Kts.
In case of loss of the ESS BUS, the ISIS indicator is supplied only from the HOT BUS (701PP) through the ESS BUS SPLY GND/FLT COND relay (7PC).
Consumption of the equipment is 20 W maximum.
Transparency time for the ISIS indicator is not less than 50 ms (memorizing of current configuration on power supply transients comprised between 50 and 200 ms).
The display is lost during power supply cutoff comprised between 50 and 200 ms.
Thought, ISIS never failed,is just reported conditiond & situation after an unthinkable event........