EDO Corp., New York, received a $44 million contract from the U.S. Air Force for AN/PLM-4 radar-signal simulators used to test the electronic defenses of military aircraft. EDO said the contract enables the Air Force to purchase about 491 AN/PLM-4 systems over the next five years. The AN/PLM-4 radar-signal simulator generates radio-frequency signals, such as those used by anti-aircraft weapons. By simulating these signals, the aircraft’s defensive electronics can be tested on the flight line before take-off, the company said. "Our PLM-4 quickly and effectively tests the radar-warning systems on virtually any military aircraft," said James M. Smith, EDO’s chief executive officer.