As an analogy, perimeter security/guards are EXPECTED to be paranoid/hypervigilant, their reporting/control systems attuned to that. Someone leading that system is expected ... +
The protected, OTOH, are expected to ease off - because they have someone to be paranoid on their behalf. Why have these systems evolved this way? +
Which means that the system affords a buffer - via IMMEDIATE response. +
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The effect of such alarms is also different on different classes of people. For trained personnel, it synchronizes response. For the general populace ... +
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Fin.