Malaysian Prime Minister Najib Razak spoke during a press conference in Kuala Lumpur, Malaysia, March 24, 2014, that new analysis of satellite data suggested that the missing Malaysia Airlines Flight MH370 "ended" in the southern Indian Ocean. He also said the type of analysis used to investigate the mystery of the jetliner has never been used before. The statement sparked heated suspicion of international media.

As the search for flight MH370 entered its third week, the U.S. military ordered the dispatch of a towed sonar, which is believed to have the ability to detect the black box, to the area where U.S. troops are searching

Chris Budde, officer of the U.S. Seventh Fleet said in a statement: “This move is simply a prudent effort to preposition equipment and trained personnel closer to the search area so that if debris is found we will be able to respond as quickly as possible, since the battery life of the black box’s pinger is limited.”

This U.S. equipment has the ability to detect the sonar pulse signal of the "black box" at a depth of 20,000 feet (about 6,096 meters). In 2009, the U.S. military used the equipment in the search for the black boxes from the crashed Air France 747.

When the locator identifies the black box signals, the location of the source will appear on the computer or the oscilloscope. Control personnel will record the strongest points of the signal, and then determine the location of the black box after repeated measurements through "triangulation" .

The cockpit voice recorder and the flight data recorder are collectively called the "black box". The cockpit voice recorder automatically records the cockpit crew dialogue and other sounds; the aircraft flight data recorder records the flight speed, direction, altitude, cabin pressure and other information.

Read the Chinese version: 为何未见残骸就确认“终结”？; Source: Beijing News