Search and Rescue Transponder

Search and Rescue Transponder

Search and Rescue Transponder (SART)

SART or Search and Rescue Transponder, is an extremely vital equipment on the ship as it performs the job of a signal-man. It is a vital machine during distress for it helps in locating the position of the vessel in case it goes off-track. SARTs are made of waterproof components which protects it against damage by water. SARTs are essentially battery-operated, hence can be operative for a long time. SARTs are of use in ships, lifeboats and liferafts. They are the most supportive machines in case of an unprecedented emergency. SARTs are designed to remain afloat on water for a long time in case the vessel finds itself submerged in water.

The bright color of SARTs enables their quick detection, whereas the combination of transmitter and receiver enables it to transmit as well as receive radio signals. SART machines have been instrumental in rescuing several crafts and ships by reacting to the search signal sent from an X-band radar, typically of 9 GHz.  These signals are known as homing signals. The response is usually displayed on radar screens as a sequence of dots on a X band-radar, which helps rescuers reach the vessels in time.

A SART is basically an electronic device that automatically reacts to the emission or interrogation by radar. This enhances the visibility of the party in need of assistance on the radar display (PPI). They operate on the 9 GHz band and only transmit, when they are switched on, when interrogated by a radar.

General features, location and functioning of the SART

  • SART is made of fiber reinforced plastic which can withstand and bear the prolonged exposure to sunlight and extreme weather conditions.

  • It is capable of floating free of the survival craft.

  • International orange in colour.

  • SART is mounted on a mounting bracket which is fixed to a bulkhead on ship, on the bridge.

  • It operates on the 9GHz frequency band (9.2 to 9.5 GHz) and generates a series of clips on the radar it is interrogated by (3 cm/X Band radar).

  • They can either be portable or fixed permanently into the survival craft.

  • The SART is activated manually and hence responds only when interrogated.
  • When activated in a distress situation, the SART responds to radar interrogation by transmitting a signal which generates 12 blips on the radar and turns into concentric circles as the range between the two reduces.
  • On the PPI, the distance between the blips will be 0.6 miles.
  • This signal is very easy to spot than a signal echo from say, a radar reflector.
  • The SART also has a audio or visual indication of its correct operation and informs survivors when interrogated by the radar.
  • An audible beep is heard every 12 seconds when there are no radars in sight and every 2 seconds when interrogated by radar.

Carriage Requirement

  • Passenger ship- at least 02.
  • Cargo ship 500 GT and above- at least 02.
  • Cargo ship 300 GT and above- at least 01.
  • 1 on each survival craft.

Battery Requirement

  • In standby condition, operational for 96 hours.
  • In working condition, operational for 08 hours.
  • Battery should be replaced every 2 to 5 years.
  • Operable in temperature between -20 deg to 55 deg.

Test Procedure

Self Test (General)

  • Switch SART to test mode.
  • Hold SART in view of the radar antenna.
  • Check that visual indicator light operates.
  • Check that audible beeper operates.
  • Observe radar display and see if there are concentric circles on the PPI.
  • Check the battery expiry date.

Self Test (Typical)

  • Remove SART from the bracket.
  • Insert probe into the SART at 2 seconds interval; the lamp flashes and the beeper sounds.
  • Observe concentric circles on the X band radar.

In case of a false activation, switch the SART off immediately. Transmit a DSC safety alert on VHF Channel 70. Transmit a safety broadcast by RT on VHF Channel 16 to all stations indicating your ID and position and that you wish to cancel your false alert which was transmitted in error.


The AIS-SART is a self-contained radio device used to locate a survival craft or distressed vessel by sending updated position reports using a standard Automatic Identification System class-A position report. The position and time synchronization of the AIS-SART are derived from a built in GNSS receiver (e.g. GPS). Global Maritime Distress Safety System (GMDSS) installations include one or more search and rescue locating devices. These devices may be either an AIS-SART (AIS Search and Rescue Transmitter) or a radar-SART (Search and Rescue Transponder).

SARTs find themselves useful in rescue operations involving airplanes or ships stranded by air and sea accidents. They are designed to survive the toughest conditions and stay active on elevated positions like on a pole so that they could cover a diverse range. Talking of heights, a SART transponder on an airplane could have a range of 30 to 40 miles. This helps to scrutinize a huge range and huge area.

Looking at the facts, one can determine that SARTs are a marvel of human engineering, making them significant equipments on the ship venturing out in deep oceans.

Read more : Search and Rescue Radar Transponder (SART) usability for ship

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