Let me take a swing at this since it also confused me - until I read (and re-read) Andy's book.
Modes determine the settings used for the various options of the way the Etrac responds to targets. These are for the various settings used in the menu headers such as: Sensitivity, Audio, Expert and Preferences. Each mode can have a different group of settings under all those headers. You have a total of 8 modes available: 4 are preset by Minelab and cannot be permanently altered, at least not under their Minelab mode names. 4 are defined by the user. You can change variables in the Sensitivity, Audio, Expert and Preferences headers and then save them for later use.
Discrimination, better referred to as
Patterns determine what targets will be reported by the detector and which will be ignored (nulling - a momentary loss of any sound - even threshold). Patterns are what allow you to use Bill S's trashy park program with great success in trashy parks and what allows you to sniff out the oldies in Andy's old coin program. But regardless of which pattern you use, the sounds (Conductive versus Ferrous; Normal, Long, Smooth or Pitch Hold; Pinpoint mode, etc.) all remain the same according to the Mode you initially selected. And if you didn't manually select a mode, the Etrac uses the same mode you used when you last used the machine. I
believe that the first time you ever turn the Etrac on from the factory, you are in Etrac "Coins" mode.
What may be confusing is that each Mode comes with its own discrimination pattern. On page 46 of Andy's book, he refers to this as the 4 Free Bonus Patterns. While the 4 Minelab Modes can't be altered permanently in the machine, the 4 User modes can be. As each user mode is defined and saved, the discrimination pattern being used at the time of saving is saved with it. So you can essentially save a total of 10 patterns on the Etrac, 4 are defined along with the mode settings and 6 are defined independently of mode settings (they adopt whichever mode settings are currently in use.).
I'll give you an example based on how I have my Etrac set up (I wish I knew how to include screen shots!):
My User Mode 1 is TTF (Two Tone Ferrous) with a completely open
discrimination pattern. Some of my settings include: Ferrous sounds, 2 tones, Normal Response, Normal pinpointing.
User mode 2 is also TTF, but with some discrimination on the non-ferrous side of the screen.
User mode 3 is all the settings of the Minelab Coins mode but using Bill S's trashy park pattern.
User mode 4 is Andy's old coin settings using my own Old Coins
discrimination pattern.
Now if I selected User Mode 1 and then selected a
discrimination pattern similar to the Bill S's trashy park program, I would get the same tone for every target. This is because I would be using two tones, but since one of the tones would be for ferrous targets which I have discriminated out by my choice of pattern, I would never hear the ferrous tone.
Now if I selected User Mode 4 and then selected a pattern of a wide open screen, I would hear every target in the ground along the full scale of multiple tones based on conductivity. In the ghost towns where I typically hunt, I would typically last about 10 minutes using this method!
Hope that helps.
Let me get on a 'soapbox' here for a second and just say that it would've been very nice to have the ability to assign our own names to both our user modes and our patterns. While I think most experienced users can visualize what targets will be likely to produce a response with any given discrimination pattern, it would be very nice to have the option of giving them names. Shame on you, Minelab, this would have been so easy from a programmer's point of view.
