Model 212-6LW is a 6 volt system that will project an adequate signal for up to sixty days on 4 D-Cell Alkaline Batteries.

Model 212-3LW is a 3 volt system that can operate on two to four D-Cell batteries. It will project an adequate signal for over 60 days on two D-Cell Alkaline Batteries and over 120 days with four D-Cell Alkaline Batteries