Alarm conditions are detected by the Scan Alarm and Control (SAC) program that runs on each SCADA server. The SCADA server sends an alarm message to each node in the network when an alarm is detected. Each alarm is over 1024 bytes in length. The actual message size transmitted by the SCADA server is slightly larger. If several alarms are detected in the same scan cycle, the SCADA server groups as many alarms as possible into a 16 kilobyte message before distributing the alarms to each node.
