Sound Powered Telephone system is used for communicating with the wheel house, the engine control room, and the steering gear room in case of emergency and for communicating between the areas or rooms when necessary. Especially, being independent from the power supply of the vessel, this system allows for emergency communication at critical spots in the vessel even in case of power failure. It is manufactured to be a waterproof and dustproof appropriate for the vessel, and adopts the input power supply of 24V DC to deliver communications and signals (bell, lamp, etc.).