Airmen Edzel Gaytano and Cody Jernberg, 364th Training Squadron electrical and environmental systems apprentice course students, change out a transformer rectifier on an F-15 Eagle at Sheppard Air Force Base, Texas. The rectifier converts 115 volts of alternate current down to 28 volts of direct current. This device is critical in operating relays or transferring power form one source to another. (U.S. Air Force photo by Senior Airman Robert L. McIlrath)