There was a lot of discussion of White's TDI on the following forums.
http://members5.boardhost.com/MetalDetecting/index.html
http://tdi.invisionplus.net/?mforum=tdi&s=7a3a21fc1e7894491788d20fb1125cb8&showforum=3
http://www.goldplacer.com/forums/viewforum.php?f=4
What created the initial buzz was the TDI had the same traits of the GS5 which was only know to a few users.
http://members5.boardhost.com/MetalDetecting/msg/1211622470.html
In that one could use the TDI in a coin shooting mode for high conductor coins and almost eliminate all iron targets as well as
small aluminium such as pull tabs. You don't dig bottle caps or pull tabs in this setting.
It is an unbalanced ground mode with reduced depth but with a 40 coin versus 10 trash target ratio it caught a lot of
people by surprise. You have to remember this is a PI and not a VLF. You can also distinguish large ferrous items from
non ferrous items- tin cans versus Al cans or iron bars from gold bars(He, He).
http://members5.boardhost.com/MetalDetecting/msg/1211955225.html
Where the TDI shined was in highly mineralized ground where VLFs had trouble with depth. The parks Steve and Reg detected with
the GS5 and TDI suddenly produced silver which was beyond the depth of VLFs in highly mineralized ground. In addition George K.
with the TDI totally whacked the VLFs in "hot" ground in CW sites which was noticed by a lot of relic hunters.
The TDI was never meant to be a coin machine but a gold nugget and relic machine.
I would highly recommend one if you are a CW relic hunter and hunt in "hot" ground. It is not for everyone and I probably
would recommend one only for experienced users.
Regarding the Pulse Devil or the most recent variety the Nemesis. Dave Emery(inventor) has not been on the forums for a while now.
He and his wife have had severe health issues(emergency room visits). I wish the best for Dave and understand where his priorities lie.
George