Edward Strickland Conrad, 56, who founded Applied Systems Technology Inc., an electronics research and development company in Springfield, died Tuesday at his home in Fairfax following a heart attack.

Mr. Conrad was born in Winston-Salem, N.C., and grew up in Alexandria, where he graduated from George Washington High School. During World War II, he was a Navy aviation cadet and attended Duke University and North Carolina State University. After the war, he graduated from Virginia Polytechnic Institute and later did graduate work in electrical engineering at the University of Maryland.

About 1950, Mr. Conrad went to work for Melpar Inc. in the Washington area. From 1963 to 1967, he worked in private industry in Florida. From 1965, when he returned to this area, until 1967, he worked for the Central Intelligence Agency.

He then founded Applied Systems Technology Inc. He ran the firm until he sold it recently for reasons of health.

Mr. Conrad was a member of the Old Crows Association, a group of electronics engineers, the International Electrical and Electronics Engineers, the Fairfax United Methodist Church and the Country Club of Fairfax.

Survivors include his wife of 33 years, Helen R. Conrad, of Fairfax; three daughters, Julie C. Davis and Patricia Jane Conrad, both of Alexandria, and Kathryn C. Ensall, of Fairfax; his mother, Pattie Mae Wilson, of Shadyside, Md., and three grandchildren.