Wireless Add-On Door Sensor, Works With All Carlon Entrance Alert Systems, Sensor Alarms You When Transmitter & Magnet Are Separated, Expands Your Carlon Wireless Chime System To Cover Multiple Entrances, Monitors Door Or Window To Alert You When Opened, For Use With Entrance Alert Models: RC3260, RC3760, RC2235, RC2260, Compatible With All Carlon Wireless Chime Systems, Battery Powered Uses One 6V Alkaline Battery Size Px28a, RC3095, Included.