It functions stolen-proof for the valuable things including person, Microcomputer control technique adopted, and it consists of two parts: receiver (master)and remitter (pickaback plane)and have numerous codes. It features convenient use, easy operation, small size, and easy to take, widely used with mobile, wallet, box, little boy, key and so on valuable cases to protect your prpoducts or little boy against lost or stolen . It also can be adjusted including distance, vibrating, alarm, safe power. It is very small and it?s frequency is 315 HZ. Detecting area is ?C100 dbm.. Descriptin 1. Please put the switch against "OFF" when it is no need so that we can extend the life of the battery. 2. Waterproof. 3. Please change the batter when the voice of the receiver is reduced.