Make-before-break contacts ensure

digital field instruments remain powered and the process

is undisturbed. Analog output signals are briefly driven by

both cards for < 5 ms during switchover of the card.

Hardware Alerts automatically report hardware integrity errors

for both the primary and secondary cards. Any event that

causes a switchover is also reported automatically through the

system hardware alerts and is logged in the Event Chronicle.

Events that can cause a switchover include.

• Hardware failure within the active card.

• Communications failure between the active card and the controller.

• Detection of a fault in the field wiring.

A switchover may also be initiated from the diagnostics

explorer, and the health and status of both cards and

their channels are available in the diagnostics explorer.

The system automatically commissions a new standby card.

In safe areas, failed cards can be replaced under power.

In hazardous areas, appropriate installation procedures

must be followed.