Arthur Enderlin, 78, a retired Navy captain who was director of telecommunication at the National Security Agency and later was a telecommunications security analyst at the Defense Department, died Sunday at Bethesda Naval Medical Center. He had leukemia.

Capt. Enderlin, who was born in Calumet, Mich., and grew up in the state of Washington, was involved in communications all of his working life. From 1910 until 1926, he worked for the Tropical Radio Telegraph Company in Panama, Costa Rica and Nicaragua. From 1928 until 1940, he worked for the International Telephone and Telegraph Company in Honolulu.

An officer in the Naval Reserve, he was called to active duty in 1940. He was the communications officer at the Navy Yard at Pearl Harbor when the Japanese attacked on Dec. 7, 1941.

During the remainder of World War II, he was a communications officer and took part in a number of campaigns in the Pacific, including Saipan, Tinian, Guam and Okinawa. He twice was awarded the Bronze Star Medal.

After the war, he returned to civilian life in Honolulu. In 1948, he was recalled to active duty in the Navy and was assigned to Washington, where he worked for the National Security Agency and its predecessor agencies. Except for a two-year assignment to Adak, Alaska, in the early 1950s, he remained here for the rest of his life.

When he retired from Navy in 1962, Capt. Enderlin was director of telecommunications at NSA. He was awarded the Navy Commendation Medal.From 1963 to 1970, he was a civilian telecommunications security analyst at the Defense Department, and fron 1970 until 1978, he was a consultant on communications to NSA and other agencies.

Capt. Enderline, who lived in Bethesda, was a member of the Phoenix Society, the Veteran Wireless Operators Association, the Navy Cryptologic Veterans Association and the Society of Wireless Pioneers.

Survivors include his wife, the former Eleanor Corson, a daughter, Allyn, and a son, William, all of Bethesda.

The family suggests that expressions of sympathy be in the form of contributions to the Leukemia Society of America, Inc.