NAVTEX broadcasts are sent:

NAVTEX broadcasts are indeed categorized by messages indicated by a single letter or identifier. This system allows for efficient and organized dissemination of maritime safety information. By assigning specific letters to distinct types of messages—such as navigational warnings, weather forecasts, and search and rescue information—mariners can easily identify and prioritize the information relevant to their needs.

This categorical system not only streamlines the process of receiving vital maritime information but also enhances the overall safety and operational effectiveness at sea. The structure helps vessels to quickly discern the nature of the message, promoting timely responses to critical navigational and safety updates.

The other choices relate to various aspects of maritime communication but do not accurately describe the unique characteristics of NAVTEX broadcasts.