The operation of AIS Search and Rescue transceivers is defined in the equipment and test standard IEC61097-14 Edition 1.
AIS SARTs use only the modified-SOTDMA access scheme specifically defined for burst transmission in low volume emergency beacon applications.
SARTs use Pre Announced Time Division Multiple Access (PATDMA) as they continuously transmit but don’t receive.
Once activated, the SART sends its position and heading eight times in a minute. The device sends the information this often to ensure that the life raft is at the peak of the wave on at least one of the transmissions, maximising range. SARTS also send the SART safety message 'SART ACTIVE' every four minutes.
SARTs do not receive any form of data, but keep transmitting data. They are designed to work in an emergency situation.