Agilent Technologies Inc. appointed Patrick J. Byrne as a senior vice president and president of its Electronic Products and Solutions Group (EPSG), based in Palo Alto, Calif. Byrne was most recently vice president and general manager of EPSG's wireless business unit, based in Santa Rosa. He replaces William Sullivan, Agilent's executive vice president and COO, who was named president and CEO, effective March 1. Byrne will assume his new position immediately.    . . .    Paul J. Fego resigned as president and COO of Photronics Inc., a Brookfield, Conn., supplier of imaging technology for the electronics industry. The changes are effective immediately. The company said it has no current plans to fill the president and COO positions, but that it is searching for a CEO to replace interim CEO Constantine Macricostas and will streamline its management structure. Photronics also announced the promotion of CFO Sean T. Smith to senior vice president. Smith will remain CFO and will play a larger role in strategic planning. Photronics makes photomasks, high-precision quartz plates that contain microscopic images of electronic circuits. A key element in the manufacture of semiconductors, photomasks are used to transfer circuit patterns onto semiconductor wafers during the fabrication of integrated circuits.