The time after initial line failure at which the UPS
begins emitting audible alarms (beeping). This timer is
observed only if the value of extControlAlarm is timed(2).
Allowed values are 0 or 30 seconds.
If a value other than a supported value is provided in a
set request, the UPS interprets it as a the next lower
acceptable value. If the provided value is lower than
the lowest acceptable value, the lowest acceptable
value is used.