explanation as to what -- and we have some visuals to show of that. you have very simple explanation as to how we figure this out, if it's actually pings from the black box. you say number one is frequency. >> yes. we're looking for 37.5 kilohertz. >> okay. >> on the screen you see two different wave forms. one is of a constant frequency. and the other one is what we call a chirp. where you see on the left side and the right side, they're different frequencies. they're varying, different amounts. so if this pinger was programmed to be a chirp, you would recognize that and it would be differentiated from anything else that was not with that particular frequency, duration, repetition rate, lots of different ways to describe it. >> we're going to have some sound of that in just a little bit. so it's either a pure tone or chirp. you said the duration of a tone burst. >> yes. the manufacturer sets how long