A deceptive decoy used by ships against acoustic homing torpedoes, the Torpedo Countermeasures Transmitting Set AN/ SLQ-25 "Nixie", is a sound generator towed behind the protected ship. It receives the sonar signals sent by the torpedo, and amplifies and retransmits them, so the torpedo senses the Nixie as a stronger target than the ship. Since the decoy is much smaller than a ship, the torpedo may well miss it, so it is not necessarily a sacrificial decoy.
The AN/SLQ-25B version extended the acoustic countermeasures with a fiber optic display LAN, a torpedo warning and a towed array sensor. Manufactured by Argon ST and originally developed for the U.S. Navy, it is used extensively by navies worldwide, both on combat and amphibious warfare ships.