The mailbox was equipped with an ultrasonic sensor and 2 microswitches. The arduino would click a relay upon detecting mail being put in, but not when mail was taken out. This was accomplished by devising an order of actions that a typical mailperson would carry out. The relay would activated a wireless transmitter that would play a tone inside a house. The arduino used the narcoleptic library allowing power draw to be dramatically lowered by powering only what was needed, thus improving battery life.