Expanded summary alarm model

For expanded summary alarms, an acknowledgment is only for a particular transition, whether to an alarmed state, to a sub-state, or a return to normal. All transitions into different alarm sub-states must be acknowledged before the overall alarm is considered acknowledged.

The initial entry to the alarmed state must be acknowledged, and the return to normal must also be separately acknowledged.

Any transition to a new alarm sub-state is treated as a new occurrence that must be acknowledged, and whose return to normal must also be acknowledged. Sub-state transitions are treated as belonging to a "return to normal group," starting with the first entry into an alarmed state when the item was previously normal.

If the item returns to normal and subsequently enters the alarmed state again, a new return to normal group is created.

Each transition must be acknowledged individually and explicitly; and the alarm is considered acknowledged only when the item has returned to normal and all transitions in all pending return to normal groups have been acknowledged.

Note: The term "summary" means "awaiting acknowledgment." Alarms in this model are also known as "ring-back" alarms.