particular, allows you to really sweep and map the bottom fairly thoroughly. you can do this out to several kilometers each site. a matter of range in where you do it is more of a matter of the size of the target. but you could do a kilometer each side in searching for this aircraft down on the bottom. >> the sonar. sorry. go ahead. >> yes. the pinger is a great instrument and it's helped us a lot. we put divers in the water to find the recorders, the black boxes, the divers using tracking in on the pinger have been able to essentially step on the recorder before they even saw it. but a pinger is short range. and as we well know, limited time. >> as you've just made reference i think to this fact. there's a great deal of discussion tonight about how the battery life of those black boxes emitting the pinger is a very short time period if at