ITU-R M.1081-1 PDF

This Recommendation provides the automatic HF facsimile and data system for maritime mobile service using digital selective calling (DSC) messages; it specifically describes system characteristics and operational procedures for setting up calls and passing messages.

These include the contents of DSC messages used to establish initial contact between the maritime mobile user and gateway, protocols and structures of messages used to pass data over the working channel between the maritime mobile user and the gateway, and the characteristics of DSC and HF modems.