Corning (GLW) agreed Thursday to sell its frequency-control business to Vectron International.Financial details weren't disclosed, but Corning said it would take a third-quarter $25 million pretax charge on the deal. Corning Frequency Control, part of Corning's telecommunications segment, was acquired in 2000 as part of Corning's purchase of Oak Industries. CFC designs and manufactures precision crystal oscillators, resonators and filters that serve as stable frequency references for a broad range of wireless and wireline communications technologies. Vectron International is an industry veteran in the design, manufacture and marketing of crystal and Surface Acoustic Wave products, Corning said. Corning has already sold off much of the telecom business it acquired during the late 1990s in a push to radically remake its focus. The company was briefly a Wall Street highflier for its once-hot optical networking gear, but the bottom fell out of that market after the tech boom deflated. The company has since spent much time moving away from communications operations. Corning, which over the last two years has sharply cut its debt and its expenses, now sells liquid crystal displays for television and electronics use, along with environmental technologies. On Thursday, Corning slipped 45 cents to $11.80.