The radiotelegraph station shall include a main installation and a reserve installation, electrically separate and electrically independent of each other: Provided, That, in installations on cargo ships of three hundred gross tons and upward but less than one thousand six hundred gross tons, and in installations on cargo ships of one thousand six hundred gross tons and upward installed prior to November 19, 1952, if the main transmitter complies with all the requirements for the reserve transmitter, the latter may be omitted.

The radiotelegraph station shall be so located that no harmful interference from extraneous mechanical or other noise will be caused to the proper reception of radio signals, and shall be placed in the upper part of the ship in a position of the greatest possible safety and as high as practicable above the deepest load waterline. The location of the radiotelegraph operating room or rooms shall be approved by the Commandant of the Coast Guard. The radiotelegraph installation shall be installed in such a position that it will be protected against the harmful effects of water or extremes of temperature, and shall be readily accessible both for immediate use in case of distress and for repair.

The radiotelegraph operating room shall be of sufficient size and of adequate ventilation to enable the main and reserve radiotelegraph installations to be operated efficiently, and shall not be used for any purpose which will interfere with the operation of the radiotelegraph station. The sleeping accommodation of at least one radio officer shall be situated as near as practicable to the radiotelegraph operating room. In ships the keels of which are laid on or after May 26, 1965, this sleeping accommodation shall not be within the radiotelegraph operating room.

The main and reserve installations shall be capable of transmitting and receiving on the frequencies, and using the classes of emission, designated by the Commission pursuant to law for the purposes of distress and safety of navigation.

The main and reserve installations shall, when connected to the main antenna, have a minimum normal range of two hundred nautical miles and one hundred nautical miles, respectively; that is, they must be capable of transmitting and receiving clearly perceptible signals from ship to ship by day and under normal conditions and circumstances over the specified ranges.

Sufficient electrical energy shall be available at all times to operate the main installation over the normal range required by subsection (e) of this section as well as for the purpose of charging any batteries forming part of the radiotelegraph station.

The reserve installation shall include a source of electrical energy independent of the propelling power of the ship and of any other electrical system and shall be capable of being put into operation rapidly and of working for at least six continuous hours. The reserve source of energy and its switchboard shall be as high as practicable in the ship and readily accessible to the radio officer.

There shall be provided between the bridge of the ship and the radiotelegraph operating room, and between the bridge and the location of the radio direction finding apparatus, when such apparatus is not located on the bridge, an efficient two-way system for calling and voice communication which shall be independent of any other communication system in the ship.

The radio direction finding apparatus shall be efficient and capable of receiving signals with the minimum of receiver noise and of taking bearings from which the true bearing and direction may be determined. It shall be capable of receiving signals on the radio­telegraph frequencies assigned by the radio regulations annexed to the International Telecommunication Convention in force for the purposes of distress, direction finding, and maritime radio beacons, and, in installations made after May 26, 1965, such other frequencies as the Commission may for safety purposes designate.