Digital selective calling and direct printing techniques in the mobile maritime service

For a variety of reasons, communications with ships on the high seas have significantly lagged behind other communications services. For example, the maritime mobile service is practically the only service where manual Morse still constitutes a major part of the communications services. In the last few years, however, some new techniques have been developed which promise to improve maritime communications. This paper provides a background discussion of maritime mobile communications and describes two recent techniques, digital selective calling and direct printing in some detail, together with their impact on maritime communications and safety at sea. Finally, the status of and procedures for international acceptance and standardization are discussed, and national efforts to promote acceptance of these techniques are described.