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E-TRAC - Two Tone Ferrous… unlocking the "mystery" Part 2

April 08, 2011 03:36pm

Randy Horton
Randy Digger Horton

In part one I explained what ‘Two Tone Ferrous’ (TTF) is and how it works. In part two I’ll explain why I use it…

For me, deciding whether to use ferrous tones or conductive tones depends on the amount and type of "trash" at each site. As a coin-shooter who hunts old farm sites, I believe there are instances where TTF is the optimum choice.

If I am hunting an old farm site with an abundance of iron trash, I run a fairly “open screen” using TTF (little or no discrimination). A low tone is provided for all targets with ferrous readings of 18 or higher. The low tone allows me to sort those high ferrous targets out “by ear”, and ignore them, without having to look at the meter. On the other hand, if I am in an area with the typical "non-ferrous" trash (pull tabs, foil, screw caps, can slaw, etc), implementing two tone ferrous would require me to look at the meter every time the (17 or lower) ferrous properties of those targets produced it's high tone. In these particular sites, I prefer multiple tones in the conductive mode as it allows me to sort out many of those targets “by ear“, based on the sounds representing their conductivity value.

Seting TTF on the E-TRAC metal detector

Whether I monitor ferrous tones or conductive tones, as well as making a determination as to the number of tones I use to accomplish my objective, is site dependent. Some people like the two tone "dig or not" mode. Others like hearing more audio information. I happen to be in the group that likes to hear as much information as I can, without inhibiting my ability to separate and decipher each tone. That is why the number of tones I chose to hunt with is dependent on the amount and type of targets I must monitor with each sweep of the coil. Having the option to audibly monitor either the ferrous properties or the conductive properties allows me to choose the mode that requires the least amount of “meter watching“. My personal choice…? an abundance of ferrous targets = ferrous mode with two audio tones. An abundance of conductive targets = conductive mode with multiple audio tones. Your choices may vary, depending on your familiarity with the E-TRAC metal detector and the type of hunting you do.

I hope this unlocks the mystery surrounding the use of TTF on the E-TRAC. If you study the functionality of the E-TRAC, you’ll see that it is no mystery at all. It’s not for everyone nor is it for every site. But if you hunt old sites with lots of iron trash and haven‘t tried it, I encourage you to give it a shot. You may be surprised at how detecting with an open screen in TTF can increase your number of good finds. 

Randy Horton (Digger)
You'll never know for sure......unless you dig it!


Great article Digger! Everyone seems to think its the two tones and switching to ferrous that is doing the trick meanwhile it basically come down to all metal mode as we would say with the X-TERRA. When i read your article on the 705 and made the switch to AM mode it was hard at first dealing with all the sounds but my "good" finds increased 2 fold. Maybe one day discrimination will help as much as it hurts...
Posted By: antandshell on May 10, 2011 04:58am
Thanks for the compliment. And I'm glad to hear your "good" finds have increased 2-fold. As to discrimination helping as much as it hurts..... having audio tones for each notch segment does that. Its just audio instead of visual. Whether on the X-TERRA or the E-TRAC, having different tones for different targets, or target groups, allows your ears to select the targets you want to dig, by their distinct audio tones. As you've discovered, blocking out or rejecting certain targets does not cause your detector to ignore them. Rejection stops those targets from producing an audio response and creates a situation where target blanking can mask good targets. That is why "opening up" the screen usually increases our good finds. Regardless of the amount of discrimination used, the targets are always detected. We can prove that by looking at the TID when a target "blanks out" on a rejected target. It still shows the target "number(s). We just don't hear those targets that have been set to reject. And that is precisely why my preference is to hear all the sounds and let my ears do the discrimination. Especially for the types of sites I hunt, using TTF.
Posted By: Digger on May 10, 2011 12:02pm
Is there any truth to the claim that reducing the number of tones to 2 speeds up the processor in a noticeable way?
Posted By: RyanChappell on May 16, 2011 04:24am
I've not found a noticeable difference in processor speed, regardless of the number of tones being made available. Once the E-TRAC processes the target and prepares to send the tone, there is no additional filtering required. At that point, it's just a matter of selecting a tone, (based on either ferrous or conductive values) that you programmed via your settings. It may seem as if the "reset" speed is quicker, when using TTF. But I believe that is due to most of us "opening up the screen" in TTF, and hearing tones instead of the nulling we would hear if the target had been rejected. By slowing down the sweep speed of the coil (which we should all be doing in areas with multiple targets) processing "one tone for each target" shouldn't be a problem, regardless of the number of tones available. JMHO HH Randy
Posted By: Digger on May 17, 2011 01:09am
Ryan, thanks for your comment above. I'm from Minelab Engineering so would love to hear in what way the processor speed appears to be faster using 2 tone ferrous so that I could properly address the issue. Without that I'll just talk about things from the point of view of the E-TRACs internals.

Fundamentally the speed that the signal is processed in the E-TRAC is unchanged irrespective of discrimination pattern or tone mapping. The bulk of the processing time is consumed by filtering the raw channels, calculating the Ferrous and Conductivity values, removing the effects of ground etc. Things like discrimination pattern and tone mapping just force the E-TRAC to make some fairly simple decisions based on the results of some complex calculations.

It is possible however that changing those settings may change the way that the audio sounds and so appear to be faster.
Posted By: Phil on May 17, 2011 06:02am
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