Its an interesting thing to get into and I was trying to figure it out when I first bought my 396, but as I listened more and more to my radios I started to recognize different tones for different agencies. One thing I haven't played with is regenerating those tones myself in a tone generator, I'm not sure off hand how the tone out function works, but I remember it has to do with the specific sound frequencies. I might be able to come up with some specific tone frequencies, for specific agencies. Now on the other hand and I guess why I don't use the tone out function, is that when the tone out function is enable you cannot use it as a scanner at the same time. Its a great function don't get me wrong, especially if you are a fire fighter and need a pager of some kind.