Doors and windows that can be used as entrances and exits are the weakest points in the security of your home. An unprotected door or window is like an obvious "Welcome" sign for a thief, so the Sensors of Door/Window are also known as the "Entry Sensor" . As one of the most popular home security devices, the Sensor of Door and DW2-RF Wireless Window is smart enough to know if your door or window is open and you can not only send alert notifications, but also notify you when the entry point is opened, ensuring the security of your home.