Wireless Door Window Open Sensor

This door sensor should be used together with a wireless receiver(not included). Each wireless doorbell receiver can pair up to 50 sensors and each sensor can add unlimited receivers. Parameters of Door Sensors Battery Type: CR2032 cell battery, 3V (Not Waterproof) The range of two sensors less than 0.4 inch, indicating that the door or window is closed. The range of two sensors more than 0.4 inch, indicating that the door or window is left open. Package 1 * Magnetic Door Sensor 1 * button battery(1*CR2032 battery)