Search and Rescue Transponders are only ever used in emergencies. SARTs enable a rapid rescue from vessels in distress, or from lifeboats that have been launched. AIS SARTs are relatively new technology compared to radar SARTs; they enhance the safety aspect and aid rapid recovery as the heading and speed of the life raft is included in the transmissions. Rescue vessels are then able to plan a course to intersect the life raft quickly and efficiently.

IALA and ITU regulations specify all SARTs should come complete with a pole and 10 metres of string enabling easy installation onto any life raft, whether it is a powered boat or a non powered raft. According to the regulations, SARTs must be able to be seen quickly, therefore they must be high visibility yellow or orange coloured. Their lifespan must also be for a minimum of 96 hours once they have been activated.

Key to deciding which SART to buy is the antenna and batteries. The antenna must give the largest range possible; SARTs work by sending eight messages a minute, regardless of their position on the AIS slot map. This is based on the assumption that one of them will be at the peak of the wave, giving maximum range.

When AIS SARTs were first introduced, their batteries were constructed using hazardous chemicals which made them unsafe for air freighting across the world. This caused problems if you were in a remote part of the world and your supplier was in a different part of the world. However, most new SARTs on the market now use safe chemicals which are able to be freighted.

Changing the batteries in SARTs can also be troublesome as SARTs are sealed units. Some batteries are replaceable onboard, but some need to be sent to the manufacturer to be replaced, that is even if they can be replaced at all. Some products enable sailors to change the battery by keeping the battery outside the sealed area. However, some are either not replaceable, or must be replaced at an international service centre or by the manufacturer themselves. This means sending the unit back to have the batteries replaced.

When purchasing a SART, you must consider:

• It's size
• Price
• What accessories are included
• What the user interface is
• Whether the batteries are replaceable or not
• If the batteries are non hazardous
• What approvals come with it