Bluelab PROEXBOX External Lockout Alarm Box for Bluelab Pro Controller Connection to Float Switch or Alarm System Used for Water Hydroponic System and Indoor Plant Grow Allows Bluelab Pro Controller to pause dosing during feed out to minimize the risk of overfeeding and fertilizing; General uses include plant grow tent and hydroponic system Designed to connect the Bluelab Pro Controller to external switches such as a float switch, a float level sensor, or a greenhouse alarm system to check the water level in your nutrient tank and reservoir Protect and put your growing plant safety first; Pro Controller is placed in lockout mode when the switches are activated, so no further dosing will occur until reset Try Bluelab pH pen, TDS meter and other hydroponics testers for full garden nutrients monitoring in water and soil; KIT INCLUDES: Alarm Box only, Bluelab Pro Controller sold separately