SART stands for Search And Rescue Transponder.  A SART is meant to help rescuers locate you in an emergency situation.

 

When activated a vessel (or rescue helicopter) that is equipped with a 9Ghz bandwidth radar will be able to home on your SART device.  The SART will show on the radar as a series of 12 dots.  When you get closer to the SART the dots will become bigger and bigger circular lines until they are fully closed concentric circles.  By this time you are no further than 1 mile away from the SART.

 

When spotting a SART on your radar you should check with the nearest coast station if they know about an emergency situation and offer assistance when required. 

 

When, in an emergency situation you have to leave your vessel for a life raft you should always take your SART with you.  Mount the SART as high as possible in your life raft for it to be "visible" as far as possible.