47 U.S.C. § 353: Radio equipment and operators

Each cargo ship which in accordance with this part is equipped with a radiotelegraph station and which is not equipped with a radiotelegraph auto alarm, and each passenger ship required by this part to be equipped with a radiotelegraph station, shall, for safety purposes, carry at least two radio officers. A cargo ship which in accordance with this part is equipped with a radiotelegraph station, which is equipped with a radiotelegraph auto alarm, shall, for safety purposes, carry at least one radio officer who shall have had at least six months’ previous service in the aggregate as a radio officer in a station on board a ship or ships of the United States. Each ship of the United States which in accordance with this part is equipped with a radiotelegraph station shall, while being navigated in the open sea outside of a harbor or port, keep a continuous watch by means of radio officers whenever the station is not being used for authorized traffic: Provided , That, in lieu thereof, on a cargo ship equipped with a radiotelegraph auto alarm in proper operating condition, a watch of at least eight hours per day, in the aggregate, shall be maintained by means of a radio officer. The Commission shall, when it finds it necessary for safety purposes, have authority to prescribe the particular hours of watch on a ship of the United States which in accordance with this part is equipped with a radiotelegraph station. On all ships of the United States equipped with a radiotelegraph auto alarm, said apparatus shall be in operation at all times while the ship is being navigated in the open sea outside of a harbor or port when the radio officer is not on watch.