The Maritime Mobile Service is an internationally-allocated radio service providing for safety of life and property at sea and on inland waterways. It includes the Maritime Mobile Service, the Maritime Mobile-Satellite Service, the Port Operations Service, the Ship Movement Service, the Maritime Fixed Service, and the Maritime Radiodetermination Service. These services classify the different types of marine radio communications, but they are less important for regulatory purposes than the two classifications of marine radio stations:
Together, shipboard and land stations in the marine services are meant to serve the needs of the entire maritime community. The FCC regulates these services both for ships of U.S. registry that sail in international and foreign waters and for all marine activities in U.S. territory. For this and other reasons, the rules make a distinction between compulsory users of marine radio for safety at sea, and noncompulsory uses for purposes other than safety. In addition, rules concerning domestic marine communications are matched to requirements of the U.S. Coast Guard, which monitors marine distress frequencies continuously to protect life and property in U.S. waters.
The Maritime Services have evolved from the earliest practical uses of radio. In 1900, just six years after Marconi demonstrated his "wireless" radio, devices were being installed aboard ships to enable them to receive storm warnings transmitted from stations on shore. Today, the same principle applies in using both shipboard and land stations in the marine services to safeguard life and property at sea. Both types of stations are also used to aid marine navigation, commerce, and personal business, but such uses are secondary to safety, which has international priority.