47 CFR § 80.115 - Operational conditions for use of associated ship units.
(1) It must only be operated on the safety and calling frequency 156.800 MHz or 156.525 MHz or on commercial or noncommercial VHF intership frequencies appropriate to the class of ship station with which it is associated.
(2) Except for safety purposes, it must only be used to communicate with the ship station with which it is associated or with associated ship units of the same ship station. Such associated ship units may be used from shore only adjacent to the waterway (such as on a dock or beach) where the ship is located. Communications from shore must relate to the operational and business needs of the ship including the transmission of safety information, and must be limited to the minimum practicable transmission time.
(3) It must be equipped to transmit on the frequency 156.800 MHz or 156.525 MHz and at least one appropriate intership frequency.
(4) Calling must occur on the frequency 156.800 MHz or 156.525 MHz unless calling and working on an intership frequency has been prearranged.
(5) Power is limited to one watt.
(b) State or local government vehicles used to tow vessels involved in search and rescue operations are authorized to operate on maritime mobile frequencies as associated ship units. Such operations must be in accordance with paragraph (a) of this section, except that the associated ship unit: May be operated from shore; may use Distress, Safety and Calling, Intership Safety, Liaison, U.S. Coast Guard, or Maritime Control VHF intership frequencies; and may have a transmitter power of 25 watts.