Hi EC,
I think I am slowly putting it all together. Don't have all the answers yet, but I'm getting there.
At first glance when you are choosing a "# of Tones" mode to use, you may think that you are just selecting how many tones you'll hear for the tone id. You can choose between 1, 2, 3, 4, and multi-tone, Tone Id. But what you are really selecting along with the above is how you want the audio mode to process the signal response for the audio side of the detector. And along with that, two modes also change the way the visual id processes the signal.
If you go back to the manual you will find that you can choose between several audio signal processes: Continuous, sampled, or some combination of both.
The 1, 1+, and dP audio modes use a continuous signal process for the audio. You get to hear the entire signal from leading edge, peak, to falling edge of the signal. There is no internal threshold that limits how much of the signal you hear so you get to hear everything that the target might produce. Your sweep speed combined with the signal strength and target position under your coil is the only limiting factors as to how much information the audio can convey.
The 2+ mode uses a split sampling process. Continuous for the high tone side, but a combination of continuous and sampled for the low tone iron side. One aspect of 'Sampled' means that there is an internal threshold that has to be reached in order for a signal to produce a audio response. This gives you a nice long audio look at the non-ferrous signals, but helps to keeps the ferrous responses short. This in combination with the Biaxial coil is what makes this mode so good in the iron.
The 3 and 4 tone modes also use a combination of continuous and sampled signal processing. It works just like the 2+ ferrous response mentioned above, except it affects the entire discriminatory range.
The 3b mode also uses a combination of continuous and sampled signal processing but with a tighter threshold on the sampled side that requires a more stable peak signal response.
The Visual ID side only uses a sampled signal process. It works on a different sampling process than that of the audio modes and is the same for all audio modes but one. When you chose the 3b audio mode, you are also selecting to use a Visual ID mode that uses a tighter sampling process for the visual id. This is probably the least independent mode you can select and I tend to think that the same sampling process is used for both the audio and visual id modes.
I have thoughts that the dP mode also changes the visual id sampling process just by the amazing way the audio can sound so good, yet not give a visual.
So...what does this mean? Well to me, it means that I do more than just select how many tones I hear when I select an audio mode. It means I'm selecting how much or how little of the signal information I want the machine to put into my ears. Better machine control for the site, and better control of the information I'm feeding my ears and eyes. All resulting in better dig/no dig decision making.
Thats where I'm at right now.
HH