[jyl]

Originally Posted by Aurel

This.

Once active, the Dukane DK120 emits a pulse once a second that can be detected by sonar equipment up to two nautical miles away. The beacon works at a depth of 20,000 feet — far deeper than the waters where officials believe the Malaysian plane went down.

Read more: Malaysia Airlines Black Boxes - Business Insider

But has a sensitive sonar array come within 2 miles of the beacon? Big ocean, little ships.