Joseph E. Blackburn, vice president of Chesapeake & Potomac Telephone Co. of Virginia, has announced he will retire March 31. Blackburn, a 27-year C&P veteran who has overseen operations in Virginia since August 1983, will be replaced by Hugh R. Stallard, an assistant vice president who also has been elected to C&P's board of directors. Blackburn is a Lynchburg native and served in the Virginia House of Delegates before joining C&P in 1957. Stallard, a Norton native, joined C&P in 1959.

Communications Satellite Corp. has elected Edmund R. Bartlett III as its treasurer, with responsibility for financial planning, treasury operations and risk management. Bartlett, most recently vice president and treasurer of Satellite Television Corp., the former Comsat subsidiary, will report to Bruce L. Crockett, Comsat's vice president for finance.

Comsearch Inc., a communications engineering and consulting firm with offices in Reston and Richardson, Tex., has named Michael K. Morin to the new position of general manager with overall responsibility for the company's Reston operations. He previously was vice president in the firm's mass media services division.

The directors of the Public Broadcasting Service elected six new vice presidents at their recent semiannual meeting: Daniel C. Agan, vice president for advertising and promotion; Dee Brock, vice president for adult learning services; Barry O. Chase, vice president for news and public affairs programming; Amy S. Fleischman, vice president and comptroller; Lance W. Ozier, vice president for program administration and information, and Michael B. Soper, vice president for development. In a separate action, Carla Merriman was appointed director of advertising and creative services.