AC Adapterfor Water Cop moisture sensors (not included). The water detector devices or Freeze detectors are not included. These water alarmand freeze alarm units are made for use with the Classic Water Cop moisture and freeze sensors. Save on batteries if you have AC power near your moisture sensors. UL listed AC adapter cannot be used if batteries are installed in the water sensor units. For use with new Single Probe or Double Probe moisture sensors, the plug into the sensor must be removed and the units hard-wired together.