Signs and alarms come in such a multitude of forms. Consider the many varieties: warnings; cautionary statements; declarations of horrible consequence; specific directives, requirements and prohibitions; illustrations; lights, strobes, flashers and rotating beacons; bells, horns, whistles and sirens.
Consider the amount of thought, creative innovation and testing that has gone into this form of communication. The intention of which is to prompt some type of behavior, whether action or inaction: