Search And Rescue Transponders (SARTs) are mandatory carriage safety devices that form part of the Global Maritime Distress And Safety System (GMDSS). SARTs are active radar transponders, and operate exclusively in the 'X-band' part of the radio spectrum, receiving and transmitting at nominally 9,200 MHz to 9,500 MHz.

They are deployed during maritime emergencies as an aid to rapidly locating survivors who may be adrift in a life raft. Many studies have shown that rescue time is absolutely critical in minimising loss of life after abandoning ship. The conditions aboard a liferaft can be unpleasant and disorienting!

Once activated, a SART ‘listens’ for an incoming radar signal from a passing vessel – note that this can be from ANY vessel or aircraft equipped with a standard X-band radar set, and is not restricted to specific Search & Rescue craft.

When the SART receives a valid signal, it switches into Transmit mode, and responds to each valid signal by transmitting a series of twelve (12) sweeps through the band 9,200 to 9,500 MHz, each transmission lasting just over 100 microseconds in total. This signal is seen on the passing vessel’s or aircraft's radar screen as a line of twelve dots, with the SART position being given by the closest dot. This is a clear, unmistakable, Internationally recognized signal, and shows the presence AND location of a vessel, survivor or life raft with an active SART.