Jack I. Ellmann, 78, a retired electrical engineer, who had operated his own firm in Georgetown, died June 7 at Fort Lauderdale, Fla., after a heart attack.

He had moved there after retiring here in 1969.

Born in Poland, Mr. Ellmann came to this country as a child and grew up in Philadelphia.He graduated from Drexel University in 1919.

He came to Washington in 1932 and established Ellmann, Inc., now called Ellenco in Brentwood. He held many parents on electronic devices and manufactured signal systems and fire-alarm equipment. Mr. Ellmann served as an engineer officer in this country with the Army Air Corps in World War II, and in Greenland with the Air Force during the Korean conflict.

He was a former president of the D.C. Society of Professional Engineers and a life member and past national board member of the Institute of Electrical and Electronic Engineers.

Mr. Ellmann belonged to the Society of Fire Prevention Engineers, the Almas Temple Shrine here, the Disabled American War Veterans and the American Legion.

He is survived by a daughter, Susan Birnbaum Feinman, of Potomac, and three grandchildren.

The family suggests that expressions of sympathy may be in the forms of contributions to the American Heart Association.