171019-N-BN978-007 GREAT LAKES, Il (Oct. 19, 2017) Student from Electronics Technicians and Fire Controlman "A" School prepares to troubleshoot the radar simulator partial task trainer (PTT) at Center for Surface Combat Systems Unit Great Lakes Oct. 19. Over the past year students have been utilizing the PTT system after a a complete overhaul of the equipment. (U.S. Navy photo by Brian Walsh/Released)