area. it can go down to 20,000 feet below the surface. for hours and miles at a time it's listening sbenintently for black box. >> how far away? >> the outside edge is two miles. it can defect the sound. >> reporter: if the pinger's battery is fading it can still detect it. >> the signal will come up. you can see here's a cable. it runs up through the umbilical and comes into our receiver unit. we have a speaker on here and all the power buttons. we adjust the frequency. out of this box we have a computer set up that represents the si the signal from the beacon. >> reporter: a team on deck deploys other saassets. once the toad pinger locater finds the black box, this is the