The notification Id of the alarm. The high-order byte is
the card number of the card from which this alarm originated.
The low-order 24 bits contain a sequence number which increases each
time an alarm is generated. Thus, this id provides a simple way of
uniquely identifying an alarm as well as the order in which alarms
are generated on a card. For cross-card ordering, one
would have to look at the time stamp (see dateAndTime).