U.S. Air Force Reserve Staff Sgt. Isaac Maraspini, 445th Aeromedical Staging Squadron biomedical equipment craftsman, and Senior Airman Ryan Walker, 445th ASTS biomedical equipment technician, test a pacemaker during their tour of USAF Hospital Langley at Langley Air Force Base, Va., July 21, 2014. During their tour, the Reservists completed biannual refresher training to remain mission-qualified. (U.S. Air Force photo by Airman 1st Class Devin Scott Michaels/Released)