The DDD is to be tied to the net and is activated when it contacts water. It produces random ultrasound frequencies oscilating between 2 and 500 KHz, to avoid habituation to the signals.
The device has a logic part with a 16 bits microprocessor which controls the automatic switch-on when sunk in water, the low battery alarm, the power circuit command randomizing the output signals and the power part with the output transducers.
The DDD is actually used in most of the world's oceans and seas by fisheries and fish farms. Excellent results have been reported avoiding mammals by-catch and damages to the nets and to the target catch.
Even though the DDD was studied to be effective with dolphins, some customers reported good results also with killer whales, other whales, manatees, sea lions and seals.