This small burglar alarm from Yale is ideal for single rooms. However it is fully expandable by using touch and link technology. It works by detecting motion, and has a loud 100dB+ siren. Battery operated, it takes 4 x AA batteries, which are not included (Order 100-4179). It has easy, wirefree installation and can be wall-mounted or free-standing. It has a 4-digit, programmable security code.