CORNING, N.Y., Feb. 11 -- Corning Inc. has appointed three of its executives to key posts at Oak Industries Inc., which Corning acquired on Oct. 28, 1999. Robert B. Brown, vice president of manufacturing and engineering for Corning's Opto-Electronics Group, has been named president of Oak's Lasertron subsidiary. Lasertron manufactures pump lasers used to amplify optical signals through communications networks.Robert L. Ecklin, Corning's executive vice president of Environmental Products and corporate marketing, has been assigned overall management responsibility for Oak's three other business units: Gilbert Engineering Co., Oak Frequency Controls Group and Harper-Wyman Inc.Howard J. Zingler, a division vice president at Corning, has been named deputy general manager of Oak Industries. Zingler has served in a number of financial roles at Corning; he will report to Ecklin and will work with the presidents of the Oak subsidiaries -- excluding Lasertron -- to manage relations between the units and Corning.