What a clever way to introduce electrical circuitry to students! This kit includes everything you need (except 2 AA batteries). A plastic trigger plate mechanism keeps the alarm from going off, but if an 'intruder' opens the door, the plastic plate is dislodged and the circuit is closed - sounding the buzzer! Comes with complete instructions and a cardboard 'Enter If You Dare' door hang tag. For ages 8+.