Web Exclusive: Testing an emergency locator transmitter

There is an intense search for Flight 370 going on right now in the Indian Ocean. If the plane crashed into water, there should have been a distress signal leading to the scene. So far, there is no evidence that ever happened. That signal, in theory, would have come from the plane's emergency locator transmitter. Gary Tuchman took a closer look at how an ELT works in air and under water.