continuous in that way. so even if they heard it partially over the course of 90 seconds, it would be pretty unique to the device, itself. obviously there are many things in the water that can generate sound, but this is unique in what it produces. >> the device the chinese ship used to pick up the signals is handheld and meant for divers. still to come, the flight recorders, the black boxes that hold voice and data may be the equipment to help us unlock the mystery, but just finding them will not be enough. those recorders will have to be decoded. we'll show you how it is done.