Fleet Radio Unit, Melbourne (FRUMEL) was a United States–Australian–British signals intelligence unit, founded in Melbourne, Australia, during World War II. It was one of two major Allied signals intelligence units called Fleet Radio Units in the Pacific theatre, the other being FRUPAC, in Hawaii. FRUMEL was a U.S. Navy organization, reporting directly to CINCPAC in Hawaii and the Chief of Naval Operations in Washington, D.C., and hence to the central cryptographic organization. The separate Central Bureau in Melbourne was attached and reported to General Douglas MacArthur's Allied South West Pacific Area command headquarters.

Station HYPO, also known as Fleet Radio Unit Pacific (FRUPAC), was the United States Navy signals monitoring and cryptographic intelligence unit in Hawaii during World War II. It was one of two major Allied signals intelligence units, called Fleet Radio Units in the Pacific theaters, along with FRUMEL in Melbourne, Australia. The station took its initial name from the phonetic code at the time for "H" for Heʻeia, Hawaii radio tower. The precise importance and role of HYPO in penetrating the Japanese naval codes has been the subject of considerable controversy, reflecting internal tensions amongst US Navy cryptographic stations.