The status of a virtual alarm is determined by comparing the values of its sub-alarms. The outcome of such comparisons is defined in alarm logic tables built into iControl. Outcomes can be defined pessimistically (choose the more severe of two statuses), or optimistically (choose the less severe of two statuses). The pessimistic determination of a status is sometimes referred to as an OR operation. The optimistic determination of a status is sometimes referred to as an AND operation.

When you create a virtual alarm, you can specify the use of either a pessimistic or optimistic table for determining CURRENT an LATCHED statuses.When the virtual alarm is in operation, iControl uses that table to calculate the combined statuses of the sub-alarms. Where more than two sub-alarms are involved, iControl starts by comparing one pair of sub-alarms, then takes that result and compares it with the next sub-alarm, and so on.

A third type of comparison—XOR—can be used to have a virtual alarm reflect whether or not all of its sub-alarms have the same status. If all sub-alarms are the same, the virtual alarm will be green. Otherwise, it will be red.