that's when code alarm comes in handy. Instead of the typical horn honk or siren that no one pays attention to, a code alarm will honk the horn in a random sequence as if someone were honking it to get your attention. They work good too, when I lived at the apartments someone tried to get in and as I was walking out to check it everyone else in my building was stepping outside as well. I heard "what the hell is that?" out of a few mouths.