Hidden alarms and frozen outputs
Occasionally, when a disabled alarm point is re-enabled, it goes into alarm immediately or shortly thereafter, for example, when a call point is still in operation or smoke is already present in a smoke detector. This cannot reliably be determined ahead of time.
To prevent unwanted activation of alarm outputs from hidden alarms, all alarm output groups are temporarily frozen for 60 seconds whenever any items are enabled. If multiple items are enabled, the period lasts 60 seconds after the last item is enabled. This frozen condition is indicated on the MONITOR tab as a reminder.
If any alarm event occurs during the 60 second frozen period, the ALARMS tab turns red and the alarms are displayed as normal. However, none of the alarm output groups activate (although the ALARM DEVICES ACTIVATED indicator may be on). The 60 second period provides enough time to disable the alarm point on the ALARMS tab and reset the alarm condition. Once this is done, nothing happens when the 60 second frozen period lapses. The cause of the hidden alarm can then be investigated.
Note that during the 60 second freeze period, the status of the alarm output groups does not change, i.e., these outputs remain on or off as they were at the start of the freeze period. When the 60 second freeze period ends, the state of the output groups is refreshed according to the current conditions.