transmitters did not activate or were not picked up. so richard quest, our cnn aviation analyst who has been all over this since day one, can you explain to me what elts are and why this is so bizarre? >> so the elt, the emergency locator transmitter, this is different to the pingers. the pingers are designed to continue to transmit a particular signal on the recognized frequency that we have been talking about for so many weeks. the elts are designed to send a signal to a satellite in the event of an impact. they are not only used by planes, they are used by ships. they are even used by expeditions any time where if you were to get into trouble, you would need to send an emergency signal. they are picked up by satellites. they are processed through