Signals are signals, because they are out of the ordinary. Car alarms are a public nuisance. When was the last time you heard one go off, and rushed to apprehend a stereo thief? I walked up to a car with the cardboard shade proclaiming "need Help, call Police" there was an apparently unconscious person inside. He was asleep and had put the cardboard up for shade.He was angry I woke him!<br><br>