White’s Electronics TDI - Manual (Page 22)

 PulseScan TDI Owner’s Guide
Option #
You may switch the toggle to Off. This eliminates the Ground Balance control,
the Audio Tone feature, and the selectable conductivity feature allowing the
Pulsescan TDI circuitry to handle the ground mineralization. All targets will
sound alike, but you will get better depth.
Option #
Switch the toggle to On. This activates the Ground Balance, and Audio Tone
feature. Then set the Ground Balance as noted in Chart A -
Chart A
Mandatory settings if you cannot find the ground balance point,
and wish to activate the variable Audio Feature.
# - If you have set the Pulse Delay at 10 uS, which is
recommended for average size gold, set the Ground Balance
control at approximately 8.
# - If you have set the Pulse Delay midway, set the Ground
Balance at approximately 6.
# - If you have set the Pulse Delay at 25 uS, which is
suggested for beaches, relics, or very large targets, set the
Ground Balance at approximately 2.