EPIRB, SART and AIS-SART: Understanding Maritime Distress Equipment

Technical analysis of GMDSS distress electronics: 406 MHz Cospas-Sarsat EPIRBs, 9 GHz Radar SARTs, AIS-SART ECDIS targets, and statutory annual radio survey testing.

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In modern maritime safety, emergency electronics form the primary communication link that alerts Search and Rescue (SAR) authorities and directs rescue craft to survival craft at sea. Operating under the **Global Maritime Distress and Safety System (GMDSS)**, three electronic emergency devices are mandatory across all commercial vessels: **EPIRBs (Emergency Position Indicating Radio Beacons)**, **Radar SARTs (Search and Rescue Transponders)**, and **AIS-SARTs**. Understanding the operational frequencies, satellite transmission networks, homing mechanics, and maintenance protocols of these devices is essential for vessel masters, radio officers, and marine superintendents. ## The Triad of GMDSS Distress Electronics ### 1. EPIRBs (406 MHz Satellite Beacons) - **Function:** Global distress alerting. When activated, an EPIRB broadcasts an encoded digital distress signal on **406.025 – 406.040 MHz** directly to the international **Cospas-Sarsat** satellite constellation (incorporating LEOSAR, GEOSAR, and MEOSAR satellites). - **Distress Information Transmitted:** The 406 MHz digital burst transmits the vessel's unique 9-digit MMSI number or serialized beacon ID, vessel name, and real-time GPS/GNSS coordinates. - **Homing Frequencies:** Simultaneously transmits a low-power homing beacon on the international aviation distress frequency (**121.5 MHz**) to guide SAR aircraft, along with a flashing LED strobe light. - **Deployment:** Mounted in a deck cradle equipped with an automat...