LANCASTER, Pa. (Aug. 10)—Michael D. Lockhart, former chairman and CEO of General Signal Corp., has been named chairman and CEO of Armstrong Holdings Inc., a manufacturer of interior finishing solutions. He replaces George A. Lorch, who will remain as an adviser to Lockhart and the firm´s board of directors until January when he will retire and become a consultant to the company for two years. Lorch had planned to retire by the end of 2000, the company said. He also was appointed chairman emeritus in recognition for his contributions to the firm, a company spokesman said. Additionally, Frank A. Riddick, Armstrong´s former chief financial officer who was named chief operating officer in March, will assume the additional responsibilities of president.