Shopkeeper’s Bell - used the world over let stores know when a customer has entered. Or, hang it down low and train your dog to ask to be let out. Put it in a office so you know when someone arrives. It is alow tech, low cost alarm system for someone entering a house. Or have it just because it makes a nice sound every time your door opens and closes. WEIGHT 0.2 lbs DIMENSIONS 4 × 6 × 2 in