kilohertz and repulse out every second, a short burst. so if you don t know which one is which, it would be very difficult to tell. but the interesting thing is that if you find one, it is quite likely that the other one will not be too far away depending on how the aircraft hit the water but it s quite likely that they will be within a mile of each other. and lastly, for david soucie, do these batteries weaken or is it what happens with my iphone, all of a sudden it s dark? there s two things going on. you have the repeated signal every second and then you have the frequency range as well. as the battery decreases, the frequency band will start to drop like you re changing your radio station, it will start to drop a little bit. now, as far as the second interval, it s going to try to maintain that second interval over the frequency. so both of them will degrade over time but you rarely would see it click and go off. you can see some kind of