over the last five years the alarm annunciator has seen a resurgence in popularity especially for use in iec61508 sil 1 and she (safety health and environmental) alarm monitoring applications. the modern trend is to identify critical alarms and return them from the computer screen to discrete alarm windows. this is being done for two reasons. firstly, alarm annunciators offer pattern recognition to the operators in the form of led alarm fascias instead of just providing an exhaustive list of alarms and events which the operators have to scroll through and in some instances alarms can be overlooked. secondly, the analysis of plant failure modes is leading to the separation of critical alarm monitoring and process control systems for safety reasons.