At approximately 7:45 pm, an employee was in an elevator that came to a quick stop above the balling floor. The elevator repair person was called and was enroute. There were several unsuccessful attempts to reset the system. The power supply was replaced and the attendant exited the elevator at 8:57 pm. Safety Dept. was notified at 8:36 pm and MSHA was notified at 9:11 pm.