few seconds. if they continue to hear it, then that's a good sign that there at least is a signal being emitted at the right frequency. then we need to go down and detect and study the specific location. but if they have an intermittent or a brief signal, that to me, you know, says let's be skeptical until we validate. >> all right. anish patel, appreciate that and your explanation. welcome our viewers in the united states and around the world right now. i'm fredericka whitfield. a chinese state news agency says a chinese ship detected a pulse signal with the same frequency as a black box. but there is no confirmation that this is con necked indeed to the missing plane. families of the passengers have been clinging to every piece of news hoping that it's good but there's also been a lot of skepticism as well. pauline chu is in beijing.