46 CFR 27.205: What are the requirements for internal communication systems on towing vessels?

(a) You must ensure that your vessel is fitted with a communication system between the engine room and the operating station that—

(1) Consists of either fixed or portable equipment, such as a sound-powered telephone, portable radios, or other reliable method of voice communication, with a main or reserve power supply that is independent of the electrical system on your towing vessel; and

(2) Provides two-way voice communication and calling between the operating station and either—

(i) The engine room; or

(ii) A location immediately adjacent to an exit from the engine room.

(b) Twin-screw vessels with operating-station control for both engines are not required to have internal communication systems.

(c) When the operating-station's engine controls and the access to the engine room are within 3 meters (10 feet) of each other and allow unobstructed visual contact between them, direct voice communication is acceptable instead of a communication system.