The Buoy Positioning Transponder (BPT) has been specifically designed to provide accurate tracking of a vessel relative to an underwater turret buoy or similar. High performance, long battery life, rugged design and ease of installation are important operational factors for this transponder.

A number of BPT transponders plus a Ranger 2 USBL system allow accurate range and bearing measurement of the tanker to the buoy. In addition, integral pressure sensors in the transponder provide accurate depth information as the buoy is raised for docking.

Multiple transponder addresses allow for several buoys to be installed in the same vicinity without causing acoustic interference to each other. The transponders have a long battery life, are extremely compact in size and can be easily handled by one person.

The outcome of the design is an instrument that is easier and safer to handle, has a low cost and has an extended maintenance period whilst meeting the Ex operating requirements (i.e. safe operation in potentially explosive gas environments). 

The use of a transducer mounted at right angles to the main axis of the transponder simplifies mounting by hand or ROV on the buoy structure.