47 CFR § 80.142 - Ships using radiotelegraphy.
(a) Calling by narrow-band direct-printing.
(3) Calls to a coast station or other ship station must employ the following format: Coast station identification number, repeated twice; “DE”, sent once; and ship station selective call number, repeated twice. When the coast station does not reply to a call sent three times at intervals of two minutes, the calling must cease for fifteen minutes.
(b) NB-DP operating procedure. The operation of NB-DP equipment in the maritime mobile service must be in accordance with the operating procedures contained in ITU-R M.492-6 (incorporated by reference, see § 80.7).
(c) Required channels for radiotelegraphy.
(1) Each ship station using telegraphy on frequencies within the band 405-525 kHz must be capable of:
(i) Transmit on at least two working frequencies and receive on all other frequencies necessary for their service using authorized emissions, and
(ii) When a radiotelegraph installation is compulsory, a fourth frequency within this band which is authorized specifically for direction finding must also be provided.
(2) Each ship station using telegraphy on frequencies within the band 90-160 kHz must be capable of transmitting and receiving Class A1A emission on the frequency 143 kHz, and on at least two additional working frequencies within this band except that portion between 140 kHz and 146 kHz.
(3) Each ship station using telegraphy and operating in the bands between 4000-27500 kHz must be capable of transmitting and receiving Class A1A or J2A emission on at least one frequency authorized for calling and at least two frequencies authorized for working in each of the bands for which facilities are provided to carry on its service.
(4) Each ship station using telegraphy in Region 2 on frequencies within the band 2065-2107 kHz must be capable of transmitting and receiving Class A1A or J2A emission on at least one frequency in this band authorized for working in addition to a frequency in this hand authorized for calling.