Delphi Corporation, the world's largest maker of car parts, was ordered by an arbitrator to call back about 500 workers laid off at a Moraine, Ohio, factory, the union representing the employees told Bloomberg News. The report citing International Union of Electronic Workers-Communications Workers of America spokeswoman Lauren Asplen, said Delphi must reinstate and provide back pay to the employees because of a contract provision that guarantees 1,500 jobs at the air conditioner compressor plant until 2011.