I am supposing that what Randy S. is referring to, is a target ID system which, in successive passes over the target, integrates the individual ID's to "average them out". There are a variety of ways to do this. The White's "Signagraph" system is probably the most sophisticated. Unlike the other systems I am aware of, the Signagraph takes several ID samples during a single sweep over a target, such that an irregularly shaped target produces a "scatter" of ID's, whereas something with good shape symmetry like a coin or ring produces tightly grouped ID's.
I'm unclear as to what this would have to do with the Goldquest, which as I understand it has no discrimination, much less visual target ID.
As Mr. Foster points out, demodulating several different delays and comparing the signals would provide a means for discrimination and target ID, but reliable separation of ferrous from nonferrous targets in a mono loop PI is an elusive goal.
That having been said, unreliable iron discrimination/identification can be a lot better than none at all, and I believe that in the future we'll see more emphasis on iron disc/ID in PI's.
Back in the mid-80's I built a PI that acted like a VLF/TR discriminator at poptab reject, except that unlike a VLF/TR it was unaffected by mineralization. It was really neat-- on a trashy mineralized beach, where the best motion VLF units would only discriminate about 2-3 inches deep, this PI simply ignored all the trash-- all I dug was coins. But.... it wasn't very sensitive (the consequence of having to subtract signals to get discrimination/maghemite balance); and, since it rejected aluminum trash, it would have been useless for relic hunting, or for coinshooting in places other than the <IMG SRC="/forums/images/flag.jpg" BORDER=0 ALT="USA">, where most of the desirable targets fall in or below the aluminum poptab range.
--Dave J.
