These Pura Control Modules can be used with Pura UV20, UVB and UVBB Ultrviolet water systems. These Pura UV water systems can be found and bought here on our website along with any accessory you might need for it in the future. A Lamp Out Circuit LOC provides a warning or an automatic shutdown if the lamp is not functioning for whatever reason. This protects against contamination of the system by passage of untreated water. Here are the options: 1. If you want an audible alarm to warn you of trouble with the system, order the audible alarm and the lamp out circuit. Specify NO“normally open” lamp out circuit, which is the correct system to power the audible alarm. 2. If you want the unit to shut down completely in the event of lamp failure, order the NC“normally closed” lamp out circuit plus the solenoid valve. Note: The standard Pura unit comes with a visual monitoring system that allows you to see if the lamp is not functioning. The options above serve as added safety features.