Use the Bluelab ® External Lockout & Alarm Box to connect the Bluelab ® Pro Controller™ to external switches, for example - a float switch or a greenhouse alarm system. When these switches are activated, the Bluelab ® Pro Controller™ is placed in lock out mode, so no further dosing will occur until reset. Comes with built-in alarm which can be disabled if required. It can be connected to an external alarm (horn or flashing light).