AIS Class B units of True Heading Put to Test on Volvo Ocean Race

by OldSailor on October 16, 2008



All the eight boats of Volvo Ocean Race (VOR) 2008-09 are fitted with AIS-CTRX Class B AIS Transponder of True Heading, Sweden. The AIS-CTRX is considered as the most suitable product for pleasure craft and smaller commercial vessels. The AIS Class-B transponder provides both reception and transmission of Automatic Identifications Systems (AIS) data at a fraction of the cost of a conventional Class-A transponder. All the eight boats of VOR are equipped with AIS-CTRX and Class B VHF Splitter, both from True Heading to share the same antenna between AIS and VHF to get longer range.

Some of the interesting features of AIS-CTRX Class B AIS Transponder are:

  • high performance, low cost and highly robust
  • can transmit and receive data to facilitate the vessel to see other vessels and to be seen by other vessels within the equipment range
  • has optional ‘silent mode’ to see other vessels (only to receive AIS data) and other vessels can not see
  • water resistant and can operate in harsh weather conditions
  • has built in 16 channel GPS
  • transmits every 30 seconds vessel identification information
  • has position accuracy of less than 3 metres
  • needs both VHF and GPS antenna

Here is a sketch showing Class B AIS Configuration from Australian Maritime Safety Authority (AMSA).


  1. Each AIS system requires a VHF antenna to receive and transmit radio signals.
  2. Each AIS Class B requires one VHF transmitter to transmit the vessel information onto the appropriate time slot.
  3. Each AIS Class B requires two VHF TDMA receivers to enable the vessel to receive the information of other Class A and Class B vessels in range.If supported, the AIS Class B may include a dedicated VHF Digital Selective Calling (DSC) systems receiver for channel management.
  4. The AIS unit transmits and receives vessel identification information such as identity, position, speed and course over ground which can be displayed on a computer or a chart plotter.
  5. Position and timing information is normally derived from an integral or external global navigation satellite system like Global Positioning System (GPS) receiver. Other information broadcast by the AIS, if available, is electronically obtained from shipboard equipment through standard marine data collections.

Here is an image from True Heading showing AIS data in a Electronic Chart System.


Read more about AIS-CTRX Class B AIS Transponder from True Heading and IBI News.

Do you want to take an interesting Tutorial on Automatic Identification System (AIS) from Australian Maritime Safety Authority (AMSA) ?

Click the image below to proceed. (Best viewed in Windows Internet Explorer)


Here is a video clip of AIS on Island Spirit.

Post in MarineBuzz on this day a year before:

India Commissions Tsunami Early Warning center

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