This Recommendation describes a MF/HF radio systems and a HF data transfer protocols currently used in the maritime mobile service (MMS) for the exchange of data and electronic mail on frequencies of RR Appendix 17, and on non-RR Appendix 17 frequencies, providing a similar functional capability to narrow-band direct printing (NBDP) and many other features.
ITU-R M.1798-1 FRENCH-2010 history
2010ITU-R M.1798-1 FRENCH-2010 Characteristics of HF radio equipment for the exchange of digital data and electronic mail in the maritime mobile service