Clinton Peterson, 28th Civil Engineer Squadron industrial electronic control technician, uses a voltage meter to ensure a control box is operating properly on Ellsworth Air Force Base, S.D., Dec. 22, 2011. Airmen from the 28th CES routinely check the circuit boxes at facilities across the base to guarantee boilers and heaters are working correctly. (U.S. Air Force photo by Airman Alystria Maurer/Released)