White’s Electronics TDI - Manual (Page 21)

PulseScan TDI Owner’s Guide 
GROUND BALANCE ON/OFF - TOGGLE
What it does
The Toggle Switch, located below the Ground Balance knob, is used to either
enable or disable the ground balancing function (along with the Variable Audio
Tone feature). In the ON position, the Manual Ground Balance and the Audio
Tone feature are functional.
In the OFF position, the detector reverts to a straight pulse induction detector
which hears all metal targets without audio differentiation, and has no manual
ground balance control.
How to use it
This toggle must be kept in the On position when you are able to find a
ground balance point. In this instance, you have both Manual Ground
Balance and Audio Tone. If you can find a setting on the ground balance control
where the ground noises go away, then you must leave the Gnd BalToggle on,
and select a conductivity option.
If you are not able to find a ground
balance point, and the detector operates quietly without interference no matter
where the control is set, it means that the ground is not mineralized enough to
require ground balancing. This means the Pulsescan TDI circuitry can handle
the ground without manual ground balancing, and the Gnd Bal toggle could be
turned off. In this case there are two options -