The Lloytron MIP System 3 magnetic sensor is an accessory and will not work alone; it must be paired with an MIP System chime receiver or kit. It's ideal for those who have an existing MIP System in place and are looking to add an additional/replacement magnetic sensor or for those who are new to the MIP System and purchase this product along with any MIP chime receiver accessory.Add extra security to your home or business by adding a magnetic sensor to your doors and windows. For example, inside your front door you would fix the magnetic sensor with one half on the frame and the other on the door, so that when the door is opened, and the connection between the two parts of the sensor is broken, the receiver will sound to alert you that someone has entered/exited your home. Great for use in the home, outbuildings, sheds, garages, offices and much more!The magnetic sensor has a compact, discreet design, it is battery operated and can be fixed in to position using the self-adhesive pads