NAVTEX

NAVTEX, an acronym for Navigational Telex, is an international automated medium frequency direct-printing service for delivery of navigational and meteorological warnings and forecasts, as well as urgent maritime safety information (MSI) to ships. It is a component of the Global Maritime Distress Safety System (GMDSS). NAVTEX provides a low-cost, reliable method of receiving safety information for ships at sea within approximately 200-400 nautical miles off shore. Messages are broadcasted on 518 kHz, and optionally on 490 kHz (for messages in languages other than English), and are typically received through a dedicated NAVTEX receiver. The service uses a specific format of message structure to ensure compatibility and readability. Each NAVTEX message starts with a four-character header bloc: the first character indicates the station ID, the second character represents the message content and the third and fourth characters are a serial number.