Used in case the event has not been acknowledged but the EMS supports acknowledgement for this event , or in case that the alarm has been previously acknowledged and then unacknowledged.  All alarm fields other than emsTime shall remain in that case similar to the original alarm notification.
(The emsTime is always provided as the time that the alarm acknowledgement notification has been reported by the EMS.)

Readable by NMS? Yes
Writeable by NMS? No
Invariant? Yes
