Due to the numerous accidents (incident) or close call, or near miss to the usage of Acoustic homing torpedoes, as the tech. allowed it, a wire was added to control torpedoes during the first leg of their courses.
That was at first a safety measure.
As the technology evolved, other functions were added to the control of torpedoes.
Today, the safety measures remains as shutting them down when recovery was possible or exploding them as the technology could be recovered by other country. Torpedoes tech is top secret for their homing system in ANY countries in the world.
Exploding a torpedo as a tactical defensive maneuver is also used,
as long as it is still wired.
see Advanced Defensive Tactics post in Subsim.com
http://www.subsim.com/radioroom//sho...d.php?t=207398