Door and Window Open Alarm can be installed directly on any door or window without additional wires. Fix the alarm unit to the edge of a door or window and the magnetic bar to the door or window frame. A loud alarm sounds (130dB) from the alarm unit, alerting a carer in the vicinity when a door or window is opened. Self-adhesive pad included. Supplied in pack of 3. Each unit requires 3 x LR44 watch batteries (included and fitted).