noun
submarine telegraphy
Technical term for telegraph communication via undersea cables.
海底電信は19世紀に実用化された。
Submarine telegraphy was put into practical use in the 19th century.
海底ケーブル refers to the physical undersea cable itself, while 海底電信 refers to the telegraphy system or communication method using such cables.
Compound of 海底 (seabed) and 電信 (telegraphy).