Table 57 describes the details of the A & C Previous Instances Server Facet. This Facet requires support for Conditions with previous states that still require action on the part of the operator. This Facet builds upon the A&C Base Condition Server Facet. A common use case for this Facet is a safety critical system that requires that all Alarms be acknowledged even if it the original problem goes away and the Alarm returns to the inactive state. In these cases, the previous state with active Alarm is still reported by the Server until the Operator acknowledges it. When a Condition has previous states it will produce events with different Branch identifiers. When previous state no longer needs attention the branch will disappear.

Table 57 – A & C Previous Instances Server Facet

Group	Conformance Unit / Profile Title	Optional
Profile	A & C Base Condition Server Facet	False
Alarms and Conditions	A & C Branch	False