you hear the phone ringing, you narrow down your search. >> this helped to recover record from 447 in the atlantic. the pinger locator, with a fin can listening to the black box signal. >> the outside edge is about two miles. a mile and a half to two miles away. if the pinger's battery is fading, they can still detecting it. here is a capable t am cans into the receiver unit. so, we have a speaker on here. all the power buttons, adjust the frequency, and out of this box, we have a computer set up