In accordance with Resolution 351 (WRC-03)@ the maritime community is asked to consider the use of new digital technology in the maritime mobile service (MMS) in the MF and HF bands. Resolution 351 (WRC-03) also cites that the need to use new digital technologies in the MMS is growing rapidly@ and that the use of new digital technology on MF and HF frequencies allocated to the MMS will make it possible to better respond to the emerging demand for new maritime services. It is also noted that WRC-03 has modified Appendix 17 of the Radio Regulations (RR) to permit@ on a voluntary basis@ the use of various channels or bands for initial testing and future introduction of new digital technology. This Recommendation describes a MF/HF radio systems and a HF data transfer protocols currently used in the 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. A method of providing completely transparent user interoperability is also described.